Hi George,
since you're still talking to me,

I'll summarize here the specs of the models I suggested you. Glad to hear you like the Fiat 690, I'm sending you some pics of it as well.
You can keep this info as reference, to use when (if) you decide to include these models into your set.
Lancia Esatau 864
Description: Main vehicle. 4x2 truck. Produced in two lengths.
Produced: 1947-1957 (can start in 1945 in TTD, as the project was earlier and was stopped by the outbreak of the war, and be produced until 1957, when International RDF takes over - the Steyr can't replace it)
Power: 122HP
Max speed: 60 km/h
Wheelbase: 4300 mm (short version), 5000 mm (normal version)
Space in front of front axle: 1232 mm
Space behind rear axle: 1500 mm
Length: 7470 mm (short version), 8170 mm (normal version)
Width: 2470 mm
Height: 2535 mm
Weight: 6800 kg
Capacity: 8500 kg
Lancia Esatau 964
Description: 6x2 variant of 864 (one additional rear axle, unpowered)
Wheelbase: 5625 mm
Length: 9560 mm
Width: 2500 mm
Weight: 7300 kg
Capacity: 9000 kg
Lancia Esatau 864 Tractor
Description: 4x2 tractor variant for semitrailers.
Length: 5532 mm
Wheelbase: 3300 mm
Width: 2480 mm
Height: 2535 mm
Weight: 6520 kg
Max semitrailer weight: 22000 kg
Possible cargo combinations:
Bulk freight (coal, iron ore, grain etc) on open three-axle Esatau 964.
Liquid goods (oil, chemicals, goods) on Esatau 864 with trailer (see pic). Trailer should have 3 axles.
Wood and plywood on Esatau 864 with trailer
Steel and paper on semitrailers, pulled by Esatau 864 tractor
Livestock on Esatau 864 with 3-axle trailers (this trailer should have the third axle in the center, see pic)
Valuables on short version of Esatau 864. Similar for mail.
Food ref on short version of Esatau 864.
Water tanker on short version of Esatau 864.
Goods: play with imagination. I would suggest: Esatau 964 with tarp: closed van version of Esatau 864 (see pic): closed semitrailer pulled by Esatau 864 tractor; open Esatau 864 with trailer with colored old style containers.
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Steyr 380
Description: Main vehicle, 4x2, two wheelbases and a tractor version for semitrailers. Longer wheelbase version can be a van (see pic)
Produced: 1949-1960
Power: 90HP
Wheelbase: 3710 mm (short version), 4200 mm (standard version), 3260 mm (tractor version)
Length: 6265 (short version), 7045 (standard version), 5255 mm (tractor version)
Width: 2200 mm
Height: 2127 mm
Weight: 5725 kg (short version), 5785 (long version), 6265 (tractor version)
Max speed: 73km/h
Capacity: 5000 kg
Possible cargo combinations:
Bulk freight (coal, iron ore, grain etc.): short open version.
Liquid cargo (oil, chemicals, goods): tractor + one-axle semitrailer (see pic)
Wood on tractor + rear single axle (Opel Blitz style)
Plywood on short (or standard) version with trailer if you like
Steel on open semitrailer pulled by the tractor
Paper on open standard version with trailer
Livestock on standard version
Valuables in the van version, same for mail
Food ref on long version, or on semitrailer pulled by the tractor
Water tank on semitrailer pulled by the tractor
Goods: use your imagination... I'd say: tarp version of standard wheelbase; closed van; open semitrailer for machinery; open standard version + trailer for early containers.
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Fiat 690N/690T
Description: Main vehicle. 6x2 or 8x2 truck (two front steering axles, one rear powered axle, one optional rear unpowered axle), comes in two sizes and a tractor. Hauls most of the TTD cargo and can have trailers or semitrailers attached.
Produced: 1960-1967 (this is relative to the first version: in TTD, we can make it available until, say, 1972, to represent it until its latest version)
Power: 180HP
Max speed: 64Km/h
Wheelbase: 1485+3900 mm (Long version), 1485+3000 mm (Short version), 1485+2340 mm (T tractor version)
The data above refers to 3-axle model. Long version was also available in a 4-axle configuration. Length was untouched and one axle more was put right in front of last axle (so the wheelbase changed).
Space in front of front axle: 1310 mm (All)
Space behind rear axle: 1565 mm (Long and Short), 960 mm (T tractor version)
Length: 8260 mm (Long version), 7160 mm (Short version), 6095 mm (T tractor version)
Width: 2500 mm (All)
Height: 2640 mm (All)
Weight: 7500 kg (Long version), 7300 kg (Short version)
Capacity: 10700 kg (Long version), 10500 kg (Short version)
3-axle trailer capacity: 18000 kg
4-axle trailer capacity: 22000 kg
6x2 version available (two steering axles), 8x2 available for the long version (one extra rear axle)
Fiat 682N/682T
Description: Earlier version of 690, 4x2 or 6x2 (one front steering axle, one rear powered axle, one optional rear unpowered axle), comes in three sizes and a tractor. Ought to be in the set to transport lighter stuff. Can have trailers attached.
Produced: 1955-1963 (earlier version with only one steering axle)
Wheelbase: 2926 (T tractor version), 3590 (Short version), 4000 (Normal version), 4870 (Long version) (All refer to 2-axle model)
Fiat 693
Description: 6x4 version of the 690 (one steering axle, two powered axles), comes both as a truck (693N) and a tractor (693T)
Produced: same as 690
Wheelbase: 4000
Possible cargo combinations
Bulk, heavy freight like coal and iron ore should be transported by sturdy 3-axle 6x4 693's (one steering axle), or by a 690T with the correct semitrailer (pic called Fiat_690T_semi_bulk.jpg). Maybe iron ore by the 693 and coal by 690T, or a random combo.
Grain should be transported by proper silos. I've got a pic of a 682 with trailer with grain containers (the front is an old version, it's there just to give you the idea). A two-axled 682 with a three-axle trailer (like the pic) would do the trick.
Liquid goods need tankers. You can implement many variants here. In the pics you see a long 4-axle 690N pulling a 4-axle trailer; a short 3-axle 690N pulling a trailer (should be 3-axle as well): a 690T pulling a 2-axle semitrailer; and two short 682's. The last two could be good for drinkable water, while the first three can do the job for oil, chemicals, and goods.
Wood can be transported in semitrailers, 3-axle ones should be fine. A two-axle 682T or a three-axle 690T would pull them. There's also a pic of a 682 with trailer transporting wood, though. Plywood, on the other hand, could be transported with 690N's with trailers. In the pictures you find a long, 4-axle 690N with a 4-axle trailer and a short, 3-axle 690N with a 3-axle trailer.
Like wood, steel could transported on semitrailers, maybe pulled by a three-axle 690T. Same for paper.
Livestock would require trailers. There is a model of a 2-axle short 682, you can draw other models too if you prefer; a trailer should be attached.
Valuables need a lighter truck. I'd suggest to draw a 2-axle short 682.
Goods: here you can unleash your imagination. You have lots of pics. Variants which ought to be there are: the heavy machinery transporter (there's a pic of an excavator pulled by a massive 6x4 693T); the two-axle car transporter with different bodywork; the four-axle 690N flatbed transporter with no trailer for containers; some trucks with tarp (with or without trailer); a closed semitrailer (can be used for mail, too).
If you want to draw a food ref for arctic/tropic, I'd suggest to draw a white closed semitrailer pulled by a three-axle 690T.