The 76 firebird kit is a tough one to get,
Mpc made the annual promo & kit of the 76 firebird formula in the 70's but the kit was never reissued, only the 1977 to 81 (quad lights) T/A kits where repop in the last years.
In fact, at Pontiac, the 74 to 76 where a bit less popular, but the runs from 1977 to 81 had a much bigger succes in sales, explaining why most american kit makers made at least one version of the firebird from 1/32 to 1/8 scale in the late 70's & early 80's, finding these kits is really easier than a'74 '75 or '76.
Japanese manufacturer ARII makes the 1/24 '74 T/A version, as a basic curbside kit, the rear window design is different & a few small front & rear details from a '75-'76 but could be a start for kit bashing with Monogram's 1/24 '77 T/A kit still available.Check eBay.
Hope this help's.