what make model of carb for '64 slant 225

Both Holley 1920 and Carter BBS were used in production so either would be correct. The originals used the older style bimetallic coil in the choke well on the intake manifold for the choke action, if you are wanting year-correctness. For that period, the choke pull-off is not a vacuum dashpot external to the top of the carb body as on later models; it is a choke piston within the top of the body.

This video shows an intermediate year 1920 with a choke piston but with the later electric choke action. [ame="http://www.youtube.com/watch?v=d-htTHAkBvc"]Holley 1920 Carburetor Rebuild Part 1 - YouTube[/ame]