Alright, I'll hopefully soon be joining you Thirdgenners I just got re-hired at my old job yesterday and I should be selling my car early this week to a friend which means I'm hopefully going to buy the '91 Firebird I'm looking into. Its a L03 305/5spd. I'm trying to pick up the SLP 3" cat-back setup because my friend has it on his '97 Z28, and we both love it.

Anyways, I'm going to be wanting some headers as well, and I can't seem to find any 1 5/8" headers that would work with a T-5. 1 3/4" is too big for me right now since I'm not going to be dropping the 350ci in for at least another year.

Also, I'm not so sure how this is giong to bolt up to the 3" cat-back. Can I use the stock Y-pipe and cat, or is that pretty pointless then? Is the stock cat only a 2.25" in/out design (cuz I know the exhaust is only 2.25" stock)?

Sorry for all the questions...I'm sure I could answer them myself once I have the car, but until then I have to rely on you guys

EDIT: I changed my mind on the topic and wanted to delete this but couldn't... how much power would I lose by going with 1 3/4" primaries vs. the 1 5/8" primaries for now? Like, until I drop the 350 in. Figure the L03 would get a CAI, SLP 3" exhaust, advance timing, and the ultimate TBI mods. It might be better for me to go with the 1 3/4" right away if this won't be too much of a difference because I'm planning on getting that 350 to 400rwhp+.

 

Every header kit out there for our cars will clear your T5. You can use any kit that Hooker, edelbrock, SLP, hedman, and mac. Those kits all utilize 1 5/8" primaries. You can also go with the Dynomax and flowtec kits that have a 1.5" primaries. 1 3/4" headers are overkill but will increase power over the stock manifolds. If you are switching to a 350 down the road that will need a primary that big than get them now and don't worry that you are not maximising your power output.