There are no Grand Banks in 34' or 38' sizes. Not counting their current lineup which use different hulls and are made to go fast, the traditional GB lineup consisted of 32, 36, 42, 46, 48, 49, and 52 foot boats. (I'm not counting the three 66' flops they made).
There are no GB models I'm familiar with that were called "convertibles." The GB Classic is a tri-cabin, the Sedan is a fore and main cabin only configuration, the Europa is a Sedan with covered side and aft decks, and the Motoryacht is a Classic tri-cabin with a full-width aft cabin, a configuration other manufacturers sometimes refer to as a sundeck.
In popularity from greatest to least (which also indicates the relative numbers made), it goes Classic, Europa, then a big gap to Motoryacht, and then an even bigger gap to Sedan. This is in the sizes from 36 up to 52. All GB32s were made as Sedans.
With a tiny handful of exceptions all GB32s are single engine boats. The GB 36 and 42 were available from the outset as single or twin engine boats although twins outnumber singles in both models, particularly in later years. So far as I know the GB46, 48, 49, and 52 were only ever made as twins.