i know what you mean, you just have to get creative
capri leaf springs are the same dimensions so you can use 2.8 single leafs, the same goes for the front hubs so you can use 2.8 vented discs
engine parts on the whole are the same as a crossflow with the exception of pistons
gearboxes are generally similar too with reguards to 2000e's i think the mk2 rs2000 box is a little larger and has differnt mounts
what sort of things do you want to do to your cortina?