I think engine building has changed a bunch and most guys are buying engines and the ones building are doing some of the work themselves and buying new parts like heads instead of having them overhauled.
The shop I used years ago is no longer they were in canton. I’d probably try calling a classic car place and ask who does their machine work. Anytime you bring up boats people start acting weird ;)
Found this on google
https://www.google.com/search?q=engine+machine+shop&rlz=1CDGOYI_enUS742US749&oq=engine+machine+&aqs=chrome.1.69i57j0i457i512j0i402j69i60l3.4122j0j7&hl=en-US&sourceid=chrome-mobile&ie=UTF-8#lpg=ik:!1e10!2sAF1QipPtbMuwQqNb40ViF0UOsQNrm7TwWE69xsbDctSM&trex=m_t:lcl_akp,rc_f:rln,rc_ludocids:2948726488596780283,ru_gwp:0%252C7,ru_lqi:ChNlbmdpbmUgbWFjaGluZSBzaG9wMSlOAQAAAAAASMeY6sblgICACFohEAAQARACGAAYARgCIhNlbmdpbmUgbWFjaGluZSBzaG9wkgEQYXV0b19yZXBhaXJfc2hvcJoBJENoZERTVWhOTUc5blMwVkpRMEZuU1VSNU1scHFkWEpSUlJBQqoBGxABKhciE2VuZ2luZSBtYWNoaW5lIHNob3AoAA,trex_id:juh60e