In basic design they are the same up until the aba crossflow in the mk3. But the injection id different. You have to see because intakes and stuff like that are different with different types of injections. But some will work.
so then cams, and pistons would be the same since there internal? also since the fox motor is mounted like a rear wheel drive car, would it be possible just to use its exhaust manifold or would i have to have one made?
Pistons probably but not cams. There are 2 different kind of heads. Hydro lift and solid lift. They use different cams. Do you have a fox? I'm not sure which yours is. You should be able to find an exhaust system for your car. I htink tt makes one. But check it out. I don't know if the manifolds are the same. I doubt it.And the manifolds are different between the different injections. I'd say if you wanna do engine work contact a good tuner and ask them your questions. Then they can point you in the right direction as to what to use and what works. Good luck