Re: Considering an LS swap
If you manage to overcome the handful of obstacles listed above, I would suggest you look into one of the aluminum block LS engines. An aluminum block is about equal to removing the weight of two full sized batteries from the nose of your car compared to an iron block LS.
Re-purposing a GM harness can be difficult and it has a lot of stuff in it you won't need, plus you'll need to buy expensive software to tune the factory PCM.
Look into the offerings from Fitech or Holley for LS systems. Fitech offers basic harness & ECM kits to kits that include an intake, throttle body, rails, injectors, etc. Holley offers systems for drive by cable and drive by wire throttle control. Both companies include free software to tune everything and support 4L60e/4L80e control.
Fuel supply is very important, don't even consider any of the "pump in a tank up front" systems, get a real fuel injection designed setup. While an in-tank GM fuel module is the best setup, it's costly and needs a PWM controller. From what I'm seeing, the Aeromotive Phantom system is the next best thing. Or talk to Rick at Rick's Tanks.
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1971 Monte Carlo SS454-496ci 600hp
1999 Trans Am-500hp
2003 Iszu Ascender XL Limited V8