Qjets are great carbs when overhauled correctly. By this I mean acid dipped and all passages, transfer slots, ect. cleaned out. Do your darnedest to find a AC Delco carb kit. It must be adjusted correctly, not only the air-fuel needle bleeds screws at the base, but the tension on the secondary venturis. If they open too soon (light tension) it will bog, If hard to open ( heavy tension ) then the secondaries are late and useless. If it is a CCC carb, the the metering rod dwell must be set correctly also. Find you a good Qjet builder ( somebody at a local car show or club will know one).