Question about LA cylinder head dimensions

I built a valve spring tool similar to your for my small blocks, both my aluminum IndyBrock and my W2 heads use 3/8 studs instead of the factory 5/16 bolts. I drilled the holes in the shaft to 4 1/2 inches on center, but I drilled the holes to 7/16 to give the shaft a little wiggle room with the 3/8 studs.