[CPNE]

If I recall your burb is an I6. If that is the case I would not swap in an auto until I swapped in the V8. The reason is that with engine/tranny swaps the driveshaft length will often change, and if you swap the tranny then the engine, you'll be doing this twice.

If you had a 69-up synchro 3 speed and put the 350/th350 combo in the I6 engine position, you'd have no driveshaft length issues. However your 67 has the older style non-synchro 3 speed which is shorter so a driveshaft length change is required with the auto regardless of engine and/or engine position.

I'd put in the 3 on the floor until you decide on engine/tranny combo as the v8 with auto will change driveshaft and column linkage, and the v8 with 3 speed will change column linkage and clutch linkage (and possibly driveshaft depending on engine mount position).

It's not a slam dunk any way you slice it, but having a parts donor will help.

FYI, there is nothing wrong with a 3 speed behind a small block unless you're putting in a torque monster. Your rear gears (3:73 stock) are suited for that tranny. A small block and auto would have been outfitted with 3:08 rear gears. An overdrive tranny would work nice with the 3:73's though.

Putting the floor shifter will definately "motivate" you to complete your swap as a floor shifter with a bench seat is a real PITA IMO.