Head work advice

1.70" intake
1.44" exhaust

The primo go-to source for many years (engnbldr) closed down when the guy retired some time back, so I don't know where to send you for 'em now.

Don't veer off into the weeds wasting time and money trying to hunt up nonstock valve stem diameters, etc.

Clean up the ports and pockets a bit; don't go crazy unless you're prepared to hit a water jacket and start all over again with a new head.

Hard exhaust seats are yes. A careful multi-angle grind on all 12 valve seats is a good plan. Bronze valve guides are nice but not mandatory. Umbrella-type valve stem seals are perfectly adequate.

How much to mill the head should be a matter of measurement (combustion chamber volume, compression ratio, etc), not guessing or magic numbers.