Norton Atlas Engine Rebuild

Hi,
Am about to start an engine rebuild on a 1967 Atlas. Have a few questions
1. What makes a Superblend roller bearing a Superblend?
2. Relative to the crankshaft assembly bolts, why are there two recessed nuts unlike the others?
3. Inside the time side crankcase a ball beating main is specified. Is the current thinking that a roller bearing like the drive side be used?

thanks

1) and 2)... Read this thread about crank main bearings given the name Superblend.

3) would be a guess on my part, but if you are talking about the shouldered nuts, I believe they are that way to provide clearance to get a wrench on the nuts. The other nuts are well below the rod journal and don't have the clearance issue.