I have a '91 RS 305 and I'm looking at the SLP LM1 (LT1 version) but I hear there is some fab work that needs done to fit it in a 3rd gen. I can't seem to find a guide on what to do or how to do it so I'm hoping someone here who's done it before can help out.

 

There is no guide, its going to take some welding and custom fab to make it work. Any competent exhaust shop should be able to make it work with no issue. If its an earlier LT1, 93-95 it wont be much of an issue since they have the single cat in a similar place to third gens, but wont be exact, so the intermediate will need to be modified. The later LS cars had an S pipe from the intermediate because their Y pipe design was different. The majority of the intermediate pipe and the rear section will be the same or similar enough. I have a Spintech exhaust on my third gen, the rear section is set up for a 4th gen and the intermediate is for a third, the exhaust shop ended up welding some new hangers to make it work a little better.

 

Other than hooking it up to the cat- or cat delete, I had to swap the rear hangers (they bolt on with the same spacing. I have the N10 dual cats that went into the factory V clamp connection. I had my brother weld a header 3 bolt flange on the v-connection, Then the same connection welded on the pipe from the exhaust kit. You may want to spot weld the driver's tailpipe to keep it in position (?).