Transport Tycoon Forums

I've downloaded new industry GRFs but where do I get the train cabs that transport those new materials?

try ukrs, nars, 2cc set etc... Generally any of those can supporte new cargos.

Or, if you like the original engines more than those, there's a newgrf called "old wagons, new cargos" that does what you'd expect from the name. It's available on the content service of OpenTTD.
(The train sets mentioned by cmoiromain are there as well)