583 big bore

[1997formulazM-10]

Hey guys I am putting my dads old race sled back together for him as a surprise. It's a 583 with fast twin pipes, he has told me the only Modification he had done was shave the head and run a thicker base gasket to make the pipes work better and jetting. i am going to run a 78 mm wiseco piston and have the raves cut down to match my question is how do I determine how much the head was shaved and what base gasket to run I can't see any markings on it

 

[rotaxrules]

yes there is markings on the base gasket on the back side between the two cylinders there is a series of holes punched in it like 5 holes or 6 holes they are different thickness I know alot of them used 5 hole gaskets with milled heads