Jeff's son is running the business now, that Jeff passed.
4 bore is 1.052".
Best to gauge or measure the bore, then decide on ball size required.
I own 5 of these "Tanner Moulds" and all are excellent. I spray the interiors with a moly bullet coating/lube.
They are .595", .677", .710", .724" and .740". Tell him what size you want bored and done deal.
This moly coating allows easy release and will not allow alloyed lead sticking to the blocks.