All Quadrajets that I know of have a factory counter bore in the base plate at the ends of the primary throttle shaft.
This bore is almost always not worn out by the years of use.
This counter bore happens to be .344 in diameter.
What I do is hand ream with a .344 ream and counter sink. Just to debur. It can be done with a small rat tail file if you dont want to buy a reamer.
I purchased a sheet of .015 thick Teflon sheet from McMaster Carr.
I cut small strips .375 wide by just under 1" long.
I pre wrap these strips around the primary shaft and then guide them into counter bores when assembling shaft.
I havent done a whole lot of them, but no failures as of yet.
And you dont run the risk of trashing a good base plate by drilling errors.