I'm not sure about the timing of the switch to the 'late model' Power Glide but if your tranny is attached to a 235, it is likely the less desireable early vesion. If it is the cast iron version, forget it. '63 sticks in my mind for the date of the conversion to mate up to the new 215/230/250 series of straight 6s. The '63-up version is a very good tranny and still has a slew of upgrade parts available. Still in demand by drag racers. I think you are stuck getting the adaptor reguardless of which tranny you run.
Build the 235. Great engine and can be made into a perky performer that isn't a belly-button SBC. I just rebuilt mine for my '53 Chevy pick up with all the hot mods (milled the head 0.100" for 9:1 compression, 280 cam, electronic ignition, Clifford 4-bbl intake, Fenton cast iron headers, full flow oil filter). I got the adaptor for the late model tranny and am using a 2004R OD. I used a Power Glide behind the 230cu in 6 in my son's '36 Pontiac (pictures in my photo album.).
Got my adaptor from Stovebolt Engines
Got my intake from Cliffords