I just went through the same process. My Q-jet was in bad shape, mainly because it sat with rotten fuel in it, in the woods for years before I got the truck.
It's interesting that you say you were told the carb was made for a 6-cyl engine. My C10 truck originally came with a 4.3 V6 and has this very carb on it. When someone stuffed a 350 in there, they reused the old carb. I never knew they made specific Quadrajets for V6 or V8's independently. I was never able to get my idle mixture just right with the Q-jet that came off the V6 engine while running it on the 350. I could back both screws out all the way and I was never able to get the mixture "too rich" and then turn them back in for the proper mixture. I thought perhaps this was an indicator it was made for a V6 (?) Still not sure.
Due to what I thought was lack of time, I changed over to an Edelbrock 1405, which I am extremely pleased with.. BUT.. Having to buy an adapter plate to fit the stock iron manifold, re-route the fuel line, add a regulator and fuel filter, and engineer a new throttle bracket and spring assembly, I have as much time a lot more $$ in the project than had I just sat down and learned to rebuild the Quadrajet.
Mack.
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