It probably wouldn't hurt to check the carb base for being warped with a straight edge,you could file it or put some emery cloth on a flat surface (like a table saw table) and rub it back and forth to remove any high spots..be careful no steel filings get in the carb..
OR you can use some RTV to fill in the gaps and not have to do that..
The proper base gasket for the 2 bolt style has plastic buttons made into the bolt holes ,so it cant be torqued down too much and crack the carb base..it doesn't need to be all that tight either..
I have three SBC 307's that have the 2 bolt intake ,and they have the smaller sized 2 bbl with the 1-1/4" throttle plates--they came on 283's and some 327's too..there is another version of the 2GC that has 1-1/2" plates,usually used on some 327's,350's and 400 SBC...the smaller carbs & intakes provide a higher air flow velocity thru the intake & heads and give more low end torque and throttle response..
Many stock cars run locally are (were ) restricted to using 2bbl carbs and many guys found them to work as well or better than a 4 bbl--"leaner is meaner" is a common old school race track saying!..
I have gotten close to 20mpg with those smaller carbs & intakes..
My first K5 had a 2 bolt intake and smaller 2GC swapped onto its original 350 and it ran strong..when I bought a used Holley 4 bbl intake with a Carter AFB to put on it,I was dissapointed,it no longer pulled strong from a dead stop,it would feel "flat" until it got over 2500 rpms or so,then the secondaries kicked in and it'd scoot,but it also started pinging and jerking under low rpm load ,like lugging up a hill in third gear..the smaller carb never made it ping and you could lug it down to almost stalling and it would pull strong with no spark knocking..if I hadn't given the 2bbl & intake away,I'd have put it back on!..the Carter was a fuel hog too,it went from almost 20 mpg to 12..
