is the bolt pattern for the exaust manifold the same from gen one to the ls1?

 

no

 

know where i can get the flange?

 

I'm not sure if this applies to cars, but I heard that the truck guys are modifying big block headers to fit GenIII's. I'm not sure where to buy the flange though. You could probably make one by tracing the exhaust gasket onto some metal then cutting it out(or something like that). You should be able to get the gasket from a junkyard for $1. Hope that helps some.

 

google LS1 header flanges, there are tons of sites that sell em

 

Its been done with 3rdgen BBC headers to use on an LS1. There was a pretty detailed thread on it. Should be able to find it if you search. Basically whats involved is getting the 3rdgen BBC headers, cutting off the head flanges, and welding on the LS1 flanges (and tweaking the tubes as necessary to fit up right).

Why not just use the F-body LS1 exhaust manifolds though? They flow extremely well for a cast iron manifold... most stock LS1 F-cars will LOSE power going from the iron manifolds to a shorty header, and only very mild gains with long tubes. The LS1 F-car iron manifolds are quite good. Much better than what the 3rdgens and LT1 cars got. Unless you have some talent and patience for fabrication, I'd suggest just sticking to the iron manifolds for a '98-02 Camaro or Firebird with LS1.

 

im going to weld up some turbo headers.