I've got a Railpower SD7 shell with an Athearn frame. I thought that SD40-2 trucks would fit, but not so. Any one know what trucks I should look for please? I also need glazing and handrails for it. A bit of a mission I think. Thanks.

Probably something from an SD-7/9. I know Life-Like made an SD-7/9, which I read somewhere the Rail Power shell was designed to fit. With little modification.
Lot of modellers were taking the earlier Life-Like models, and switching them with the Rail Power, because of the detail in the Rail Power shells. In Fact, before manufactures started re tooling their molds and getting more prototypical, serious modelers were switching out the original shells with the Rail Power.
I would see if you couldn't dig up a Life-Like frame somewhere.

Thanks for that. I'll have a look round and see what's out there.