R-3 has a ton of variants. wet sump , dry sump , short deck , tall deck , 48 degree , 59 degree.
The 48 degree is preferred for high r.p.m. use due to better push rod geometry. Siamese blocks will allow a larger bore.
The tall deck will allow you to run a longer stroke and rod without having to run a super tight ring package.
W-9 heads are what I am going with , and they also make a 59 degree version of those that has the valley side head bolt bosses machined away for push rod clearance.
I think the outer head bolt bosses are also cleaned off , and they are clearanced for the pushrods on the sides of the intake ports which limit how much meat you can safely remove when porting.
If I was going with 59 degree , I'd probably look at other options.......mostly due to fewer choices in intake and exhaust.