I am planning on pulling apart my newly aquired 83Z28 and going front to back, replacing, fixing, upgrading, cleaning, painting, etc everything. It needs a new exhaust. Here is my plan.

Hedman Jegs P/N 500-68470 headers
Hedman Jegs P/N 500-17470 Y-Pipe
Gutted Cat for LG4
Hooker Jegs P/N 520-16822 Cat-Back

Since I am using the LG4 cat, I know I need to modify the pipe from the Hooker system. What size Flange is on the Hooker System? Is it square or wider than tall? Also, what size primaries are on the Hedman Headers? Anyone else running a similar combo? This will be on a mild 350 Chevy, 700R4, and stock rear end.

Thanks

 

The flange is a rectangular shape, wider than tall.

 

The LG4 cat, even gutted, will be a huge restriction to the system. Dump it and get a proper 3" cat (doesn't need to be gutted) - that's what the y-pipe is made for. Get the 520-16823 cat-back, the extra $60 is well worth it. Use the 289-15622 cat, and the whole thing will bolt up together.

The Hedman primaries are 1-5/8" OD ("Camaro/Firebird 1982-92 265-400 ci, 1-5/8" Tubes/3" Collector, Shorty Header" - from Jegs website, emphasis added.)