Rochester 4GC. Better to update to an ECZ-B intake from '57 312 with around 500 cfm 4 bbl carb or a later '59 and up 2 bbl intake with a 302 Autolite 2 bbl carb.
Carter WCFB is a direct bolt on, used on Merc engines of the same year. But as Paul points out be sure it can be used with the Load-o-matic (no centrifical advance).
The T pot is a very good stock carb. Needs to be rebuilt correctly. Not hi performance but very good for stock use. I never had any problems with them. Bill