If the barrel extension was not removed and the "old barrel" hadn't been abused, you might be fine. It's fairly common to swap bolts w/o checking headspace as long as you know both parts are close to being "in spec". I'm not saying this is 100% correct, but it's done that way.
I've never had a problem switching parts on uppers known to be in good condtion. Recently, I assembled a new upper using the barrel, gas system, and handguards from a newish looking Colt. I used a new, name brand mil spec bolt and carrier and checked the headspace by chambering 10 random resized cases. All chambered snugly and the upper functions and shoots great. No evidence of excessive headspace.
Your gun, your face, your choice.