They are both M30 engines thus the same design. If you want the get the same power output as the 3.5 in your car you should build over the injection system aswell or at least the injection computer.
I'm not sure but I think the 86 735 uses the motronic injection system and the 84 the L-jetronic. So you might have to build over the wiring harnas aswell....
Good luck !
:sun: Johan