i have a new engine project underway and i have contemplated steping up the size of my head studs and possibly the main studs. (machining costs for me are free so i dont mind)

i cannot find any information on the correct size to go larger.
for some reason i cant seem to remember if it was 1/2 inch studs or 5/8's?
possible part numbers?
since im having the maching done for the head should i step up the size of the main bearing studs as well?

thanks in advance

Its 1/2" for the head. Not sure on the mains.