Head work advice

Strange how circumstances can change in just a couple days.

I'm dropping off my '70 head for a rebuild and need a little input.

Oversized valves - I've seen several different builds using different OS valves, but can't seem to find any specifics. Just so that I can give my guy some exacts, please recommend an exact size & brand (part number would help as well too), I just want to make sure we get the right thing the first go around.

Milling - what is an acceptable amount to shave while retaining the stock lower end short block? I want to bump the CR up a bit, but I may not be able to get the measurements for the lower end for an exact CR, but a safe bump would be nice.

He'll have Doug's recommendations on head work (chamfering, extra oil hole, 340 springs).

Anything else I should have him do or check?

The build thought is currently - Dutra RV10 RDP cam, offenhauser 4bbl, Edelbrock AVS2, Clifford headers for 3-2-1 exhaust, JP billet timing chain set, flowkooler water pump, Halifax tuned electronic dizzy, rebuilt my original oil pump, stock bottom end, one piece rear main seal.