Can verify, Cad 500 parts house mentioned above are a solid outfit. They sell everything you could want to hop up a Cadillac V8. Also, you can use the motor mounts from a 77-79 425 and then the Cadillac block becomes coordinated corporate mount like an Olds, Buick, or Pontiac or Chevy V8.
My bus was a 327, yet it still had the factory adapter plate to the big round bellhousing. I've got a 13" clutch in the middle of its gigantic flywheel, too. I don't know if all '65 era C60s had that or not, but the additional include of a hydraulic clutch just really made my conversion job easy.. well, it would be easier to do again, after learning by doing all the expensive mistakes I did back then :-D
