"I know now that it is interchangeable. I guess my concern is, I have a friend who has a Thompson Center he changed the barrel on and it had headspace problems. And I just want to be safe, and need to know if need a go gauge or no go gauge to check the headspace on it."

If the TC had a head space problem, it was a barrel problem, not a switch barrel problem. TC has put out barrels which had chamber problems. I know because I was the recipient of several. Generally speaking, switch barrel systems usually work well. Just make sure you have a gun that is designed for such.

There was no greater freedom than when I would leave Holiday Park Fish Camp heading my airboat west toward the Big Cypress. Fuel for 4 days, a good machete, an ice chest. No phone, no radio. Just God and me and the Everglades.