Is it really that important to have the original type screw on a 1978 750F? Will the value of the bike be so much less if you use an Allen, Torx or Phillips head screw. Which would solve the problem of not having the right tool in the future?
I have replaced all the JIS carb screws/bolts on the carbs of my CBXes, H1 and CB1100F with Allen head bolts. I doubt that any potential buyer would try to knock $100.- off any of them if I would sell.