That's exactly what I did last summer. I had break-in miles on my newly rebuilt 225. (This included having the rocker arms refaced by my machine shop to eliminate the wear grooves as he had a nice little fixture to do it at $3 each.) So in theory my feeler gages were getting accurate feels. Whether he ground off any possible heat treating I don't know.
Anyway, I drove the car, brought it home and immediately, and very carefully set the intake and exhaust while they were hot. I think I went .012 and .022 based on recommendations here. Next morning on a cold stone engine that hadn't moved overnight, I measured the same clearances and set the other 5 sets to the same numbers, cold, with the engine not running. I made 2 other marks on the damper 120 degrees from TDC to make it easy to index. Easy to move the crank around using the cooling fan.
My first car was a 273 Commando Barracuda and I still have the smashed feelers from setting those valves with a running engine 45 years ago.
