Lowdog,
You are correct on the clutch set-up. I have never used a 10.5 borg and beck though.I have always used the long style. I did one 360 flywheel for a 12" diaphram. There were already untaped holes in the flywheel. they were the correct size to tap either 3/8" or 7/16" can't remember which. I had to drill the bolt holes in the pressure plate out bigger and use allen head bolts to make it work. That set up is in my highboy thats in my gallery.There are two different 351-400 bellhousings and the diaphram clutch was the only way to use the shallower one.