Which one to rebuild.

[68imp]

Long time viewer, first time poster.
Long story short, I am working on a '68 Impala convertable 4 spd. with a '72 BBC 402, 3.73 rear.
Its currently running a Holley 750 vac. sec. I have 3 units I could rebuild, these numbers are 7045214 YB
that is already epoxied, 7045213 YA (complete); and 7043202 FS.
First question is which unit would be the most durable casting?
Second, with the above info. on the application and with cam specs of 515* lift and 216* duration, hyd. flat tappet on a otherwise very stock big block in a 4200 lb car. What recommended calibration would I run on which unit. The car will not be raced, just a cruiser that will not see 5000 rpm.
I also ordered the book to be ahead of the game  .  Great site with great info.!     

[Ethan1]

 I'm not too sure. The older Qjet's are not as good as the later model ones. Try looking for a mid-to-late '70s Qjet. APT would be a bonus.

[Cliff Ruggles]

Those three units are basically all the same froma performance standpoint.  I'd use the one in the best condition.  It will need recalbrated exactly for the application, as those 3 carbs are all later model emission calibrated units.

I'd get one of our kits, we can also supply the tuning parts.....Cliff