Jerry, due the the thick decks on 261 and the somewhat low power out even when modified,60 thousands is within reliability limits.Guys who do vintage drag racing will take off as much as .100 for whatever reasons.My "hot rod" 261 is decked .025 and a fairly stock 261 in my other trucks was decked .035. Neither one has had any problems with related to headgaskets in 6 years.You may or may nor have intake valve to piston interference depending on where the piston sits at TDC and your choice of cams. 261 stock type pistons are anywhere from .020 to .040 below the deck at TDC.