I was faced with the same problem.....if I did find a 2 groove GM 235 H/B it would more than likely be in need of new rubber and a rebuild so I bit the bullet and went with the modified 250 H/B from Buffalo. Aside from being pricey and needing to be rebalanced it works great. I didn't really care for the 2-belt over the waterpump idea so I went a different direction. By doing this, I can run a 6 blade fan and have no clearance issues with the alt, the H/B or the A/C compressor.
Another option is to run your alternator from the passengers side of the engine. I made my own mount that sandwiches the thermostat housing and runs only one belt over the stock adaptor plate mounted early waterpump onto the H/B in my 54 truck with 1960 engine. I'm running my a/c compressor mounted low on the driver'd side and off the front groove of the H/B. I have room above it to run a p/s pump off the 2nd groove in the A/C compressor.
Running one belt over the water pump eliminates all the pulley hunting and I'm sure puts less stress on the early-style pump. Several of the vendors offer a driver's side alt bracket that sandwiches the thermostat housing....I just used their idea and flipped it over. Had to add a little piece to the timing cover to make a stronger terminal mount for my alt. tensioner. I've got some pictures in my webshots album "Tips and tricks" on page 5 & 6 of the setups that might help.
Dave
