The A230 is the one you want. It was used as the standard transmission behind 340's. Remember in the early 70's a 4 speed was optional in Dusters and Demons. It is beefy enough to hold up to a small block. But....in those cars it had a floor shifter, not column shifted. And it is fully synchronized. I think the BH used was the same as a 4 speed. Could be the one with dual transmission bolt patterns but common input bearing housing diameter.
The older one is NON-synchro in first gear and the other synchro are very small and weak. It's about 3/4 scale of a real transmission and It is harder to get parts.
You may have to create a mongrel here. Adapting your column shifter to a newer transmission that was floor shifted. Be prepared to possibly having to modify your existing shifter rods to work. Also, eliminating the rubber isolators and replacing them with more precise brass or plastic bearings will help. Double shear clevises maybe.
As stated, Wayne Brewer or his son Dan may be able to help you plan this out. Also Jamie Passon does not really deal in 3 speeds. (I've asked)
My opinion.....I understand your desire to keep your column shifter but forget about speed shifting. That will kinda negate the impact of your 360. Missed shifts, jammed linkage, stuff like that is what you'll get. I'll be impressed if you pull this off.
