im in the process of masterminding a true dual exhaust system, and i got these free headers with 3" collecters but the only problem is they are from an old pontiac firebird like a 76 and i was wondering if they will fit on my 350 thats in the car now, because my old system has a ton of leaks and the catback broke off on day and i lost it(i didnt even notice go figure) so the real question is....are these going to sit right so i can begin takin the old system off next weekend?

 

No way, no how.

'76 'Bird had a Pontiac engine, your 350 is a Chevy small block. Even if the '76 was a Chevy engine (somebody would have had to have done a swap sometime), they still wouldn't fit because of chassis differences.