You need to decide what you want out of the rifle. If you don't reload, you need to locate a field/reject gauge and either ask someone to check it or google how to do it yourself. Hint - you remove the operating rod and disassemble the bolt to use a gauge.
If you do reload and want to use dies as-intended, then you would want to aim for headspace that is between a SAAMI GO and SAAMI NOGO. this is tighter headspace than a field gauge. Tight headspace is also thought to improve accuracy potential, if you are in to chasing the smallest possible groups.
You COULD adjust your reloading technique to make ammo unique to your rifle that is partially re-sized so that it chambers in a field/reject headspaced rifle, but that ammo would likely not chamber or fire in other .308 rifles.
FWIW, most military M14's left the factory over SAAMI NOGO, but under FIELD/REJECT. This is because they only fired 7.62x51 ammo with thicker bases than commercial brass and the military does not reload. They wanted the extra headspace for improved reliability in challenging field conditions. The Norinco M14 rifles generally ship with headspace more like a GI rifle than a commercial rifle.
When I breech up a new barrel (non-chromed) to a receiver/bolt combo, I set headspace about half way between SAAMI GO and NOGO. This is a great compromise that allows you to use the full spectrum of ammo (.308 and 7.62x51) while tight enough to ensure accuracy and brass life.
So short answer: yes, you need to check headspace and pick the bolt that gives you the best result. Then sell the spare.
