I have a a '55 235 in my '40 GMC. Its using a 41-54 flywheel. When I put it in I tried to time the distributor using the BB mark, but it wasn't right. I found that the triangle was the correct mark. I set it there and it runs great.
Steve

See my 1940 Canadian GMC:
http://community.webshots.com/user/ndnchf