ok so i have my 89 rs TBI with a motor that is knocking, but anyways what i want to do is an engine swap!! what i plan to put is a Vortec 5.3 or a 5.7 whatever i find first and cheap. but will the engine drop right into the engine bay, will i be able to use the tbi on it? What modifications will i have to do to the ECU. also im wondering if the t5 transmission will bolt right on it. thx!

 

Welcome aboard thirdgen.org.

Unfortunately, "Vortec" is used too broadly by GM to give one answer to both engines. The 5.7 is a "Gen I" style small block Chevy, like your 305, but the 5.3 is in the "LS" engine family. The answers to your questions are a qualified "yes" for the 5.7, but basically a "no" for the 5.3.

The TBI forum has a sticky about a budget 350 TBI swap that is based on the 5.7 Vortec engine and retains TBI (and contains the answer to your ECM question). Basically, the engine bolts into the car and the T5 bolts to the engine, but the induction will need some modification (detailed in the sticky).

The 5.3 requires a lot more work to get it into the engine bay. The T5 can be made to bolt to the 5.3, but for several reasons, it isn't a very good idea. The TBI may be able to be adapted to the 5.3, but I can't think of a single reason to go through that pain. Basically, read the LS1 swap sticky in the top section of this forum, and you'll see what is involved in the 5.3 swap. Since the 5.3 is a truck engine, pay attention to the link in the sticky that discusses starting with a truck engine.