That is what I'm worried about, valves. Wondered if valve position in the modified J head would put the valve too close to a high compression block piston. Sounds like it should be ok, I need the open chamber I think.
Dry fit the head with a used gasket, put a little playdough to get an imprint and check your piston to valve clearance.
Just as long as they open the throat up when they install and cut your new seats you should be good.
