I got my 54R head space gauges in from FireWerks. They are quick and simple to use. Made out of stainless. At 40 bucks for the set you really can't go wrong. And you don't have to remove the extractor to check head space. They are clearly etched for easy identification. Just a little thumbs up post for them. Every surplus shooter should at a minimum check the head space on an old rifle. Don't assume the seller does it or because a rifle has matching numbers that the head space is correct.
"I prefer dangerous freedom over peaceful slavery."
- Thomas Jefferson