Most of the stock blocks with 30,000 + miles on them that I have measure all had at least .0025 + clearances, with stock type replacement flat lifters or roller lifters
I have ordered and use the BB Chevy race .904 roller lifters for pushrod oiling and they do end up with a little tighter clearance on stock blocks
If your wanting to make a stock block as good as you can get it on the lifter bores have them bushed and size to fit your lifters