We should know tomorrow as I have a 4.25 bore big block. It will all work out, especially with the smaller exhaust valve as you can even use offset head locating dowels to shift the cylinder head around if need be. That and the 426 max wedge (4.25 bore) came with 1.88 exhaust valves and I have used 2.20 intakes with .680 gross lift on a 4.290 bore.