when i seen larry run 6.99 or whatever it was it was with a small motor that he had done,, i was told 470 or so,, i heard other details from jeff taylor and joe tueton as they were talking to larry about it all

the heads i did for morgan flowed 570,, i flowed them on as small as a 4.500 bore and the flow did not go down much at all as i recall,, though was a few years ago that i did them

i think you can run a bore as small as 4.500 and get it to fit,, ill have to look at it again,, but im pretty sure,,, you dont need a 2.550 intake valve to feed the smaller motor,, so you could go 2.450 and still get 540 probably,, that in itself would let you run a smaller bore,,, the exh might need to be moved off the cylinder wall for a smaller bore,,, which could be done