Just joined the group. 1968 Firebird 350.

Call Cliff up and talk to him directly. You'll need to provide all engine specs, current carb set-up, number and any drivability issues you're having.

Just slapping in needles and seats or throwing on another carburetor will just leave you chasing your tail.

https://cliffshighperformance.com/

FWIW
2 weeks ago i put a brand new aftermarket Quadrajet on a car and it ran perfect and idled perfect without any tuning.

Was it an independent shop or ordered through Jegs or Summit?

Thanks.

That is very true. There are so many different Q-jets around and you need to get one as close to OEM as possible. This site has a lot of GM carb spec sheets. You can look up what number carb came on your engine. You can also use it to select which jets and metering rods belong in your car's carb. I have taken many swap meet carbs and re-configured them to OEM specs for my particular engine. GM carb sheets