Hi from New Zealand,
Have a February build 1968 Firebird 400 auto 3.08 rear in need of carb overhaul. Engine is standard and rebuilt 1992, no piston oversize stated, no new cam on receipts so assume it's original, heads redone 1995 with hardened seats, trans redone more recently, milage in the last 30 years only 2000.
The Quadrajet has no number stamp but looks correct for the year, son of original owner claims original 7028264 carb, I'm not so sure, it has a limiting tab that only gives half throttle, see pic, carb is just leaking into manifold and has no pump shot of fuel, is running black and has started having throttle jamming issues, has backfired spectacularly on a quick restart, spark plugs very wet.
Please ID carburetor and supply a rebuild kit and any extra parts needed, also does this require an idle vent valve cover, possibly an idle vent if its easily damaged.