I'm building a B1 motor using a World 4.500 cast iron block, it has .042 restrictors in the full time oiling passage to the rockers
I'm going to start with them in place
If it is to much I'll add another restrictor in the heads. If to little I'll take the heads off and increaase the size .015 and try again. I do run .039 oil restrictors on all my BB Mopar Indy head motors
That has work well so far with both T&D single shaft and Harland Sharp single shaft roller rockers
Plenty of oil to the valve springs for cooling and not enough flooding to limit the oil return to the pan on those motors so far on the street and strip applications
This B1 build is going to be a eye opener on the oil return lines from the heads to the oil pan