i have a 1990 rs with 305 tbi in the car stock i want to put a 350 vortec in there out of a 1996 chevy truck i have the wiring harness and ecu from the truck but i want to keep my 700r4 trans what all do i need to modify in order to get this motor in the car and run

 

Reflash the truck PCM to a manual tune and use a vacuum lockup switch from BTO

You will probably get better advice on the swap from a performance truck forum than on here because the CFI swaps are rather uncommon. Most use the longblock with a better induction setup

 

You would also need the TV cable bracket from BTO. The vacuum lockup switch can also be had cheaply from TCI, and theirs is adjustable, or if you want a more complete kit with good instructions, there's the Painless version.