Slant six head

oh... and as manufactured originally, the "valve guides" on these heads, are just reamed passages in the parent casting.
The machine shop would have to ream them oversize enough to press a guide into the head, if wear limits would necessitate that. A "valve guide" is a "sleeve" that the MS would put into the head.
back in the day they used to sell valves with stems a few thousandths fatter than stock, as "service valves," and they would just directly ream the existing guide that much oversize to "square up" and make them truly round again.
I'd leave the "does it need new guides" and if so "what material" up to the machine shop. and if it winds up needing them, I'd do at least all the intakes or all the exhausts at that point.... if not the whole head. I don't know that I'd want just 1 or 2 valves in a given head with the guides replaced and not the rest.