[29racer]

Thanks for that info but it isn't the Chevy two piece seal they do the parts for. They do a one piece rubber seal and a two piece cork/ neoprene seal.
The Chevy two piece is a much larger diameter and a better seal for pressure systems. The Bouldin model A kit entailed adding metal to the rear of the crank and two aluminium carriers to take the two piece seal. I have only seen it mentioned once and that was in "secrets" magazine from the secrets of speed society. I used the rubber seal on a B crank and it lasted about 50 miles before it fell apart. I don't want to machine the crank down and be stuck with replacing the seal every few weeks!!
I can post pictures of the "A" conversion if you are interested.
Regards Simon