I just bought a re-coned A12 from a mate and its the early type with the dizzy at the front, and the motor im wanting to transplant it with is the later with the dizzy further back and the altinator on the other side.

What I want to know is what is prefured? and are all parts (cam/altinator and dizzy) interchangeable?

Thanks

Alternator and Dizzy is, but cam wont be, the early cam only has one worm drive that fits oil pump and dizzy, where as the later cam has two worm drives. you can use the later cam in the early engine as the other worm drive becomes redundant. Sometimes the engine mount placing can be different between early and late, but thats more of an issue when going to an A15. Be aware that the mounts that bolt to the block can also have different profiles so don't throw anything away.

The engine will run fine if you use a late cam in the early block, but the fuel pump eccentric is in a diferent position so you will not be able to run an original fuel pump.

Interestingly, the pump was moved because the eccentric was in the exact location where they needed to put the additional gear that is used to drive the distributor in the later engine.
[I just compared the two cams side by side]