If you are buying one from a private party and not able to lay eyes on it , make sure that it has provisions for wet sump oiling if you intend to go down this road.
Some also came with no motor mounts and some had lightening holes in the bell housing area than may prove problematic for tech if you go drag racing with it.
Cam bores are for R-3 ony babbit bearings , 50 m.m. roller and 60 m.m. roller.
I haven't seen SBF mains , but it doesn't surprise me at all.
The book " How to build big inch small block MoPars " goes into a lot of R-3 details.
Shady Dell's web site has a lot of info on them and the W heads too.
I believe Indy 360's can be had with the extra head bolt bosses too.
I like what I am seeing from the Ritter camp.
Very nice indeed.