Mike:
According to Leo Santucci's book "Chevrolet Inline Six-Cylinder Power Manual" (you really need to own a copy!) the block deck heights are as follows:
Standard Duty/Low Deck (230/250) is 9.150 inches +/- .007
Heavy Duty/Tall Deck (292 only) is 10.875 inches +/- .007
I suspect several of the good piston manufacturers can provide the proper pistons for your application with domes to match the Chevy inline head. Ross is one manufacturer that comes to mind. Of course, these are not what you'd call cheap . . .
Hope I have this right and that it's of some help.
