hello, well i guess a brief history before i ask my question.

i previously owned an 89 iroc and a 91 rs. i pulled the 5.7 tpi out of the iroc, the body was in bad shape, and was getting ready to rebuild it and drop it in the rs. the rs was projected to be a race only pro drag car. how ever while deployed in the past 2 months my motor and rebuilt race 700R4 transmission was stolen. and the rs was towed by the city inappropriatly. so now i have no car and no powertrain. i guess i am now planning on obtaining another third gen body and dropping in an LS3 mod crate and T-56 in it. ok finally to my question, i need to know what needs to be modified in the engine bay to accomidate the LS3. i know i need all the wiring and everything, i will take care of that later myself, i would just like to know what all needs to be modded for it to fit. i did a search for LS3 swap and wasnt able to find anything. this ships internet takes for ever to load pages.

 

Welcome aboard thirdgen.org.

Start with the LS1 swap sticky in the top section of this forum. Most of what you need to know is in there. You'll have some drive-by-wire issues that aren't covered.

 

i can't help you if you keep drive by wire. But should you decide to get rid of drive by wire, Holley makes a 90mm cable throttle body. We used it on an ls3 swap into a 99 SS last year. Only thing that needs to be modified is the k member. The ls3 pan will not clear the k-member and depends if you want a/c or not. The ls3 pan is very similiar to the fbody pan except its curved in the front which means you'll need a slightly larger notch. Or you can always just go with a tubular k-member.

 

so if the ls1 swap info should work, the ls1 and ls3 share the same block?

 

Exterior of the block is identical. Same mounting, trans flange etc.

Insides are a little different. How else would the general be making more power right?