I've just picked up an incomplete unit twin bottom end with what appears to be a good pair of matching undamaged crankcases.
Engine number is A50R 13*** which I'm thinking means 1966 model year.
DS main bearing was a lipped roller which I believe was introduced for 1966.
I have a late type crank from an A65, and also a set of 5/16" stud type A65 barrels/pistons.
Is there anything that would stop me building this back up as a 654cc twin ?