I recently built two AK 74's from a kit.  One had no issues with headspacing when the barrel was reinstalled.  The other had a good headspace prior to removing the barrel in order to install the trunnion in the receiver, but had excessive headspace after the barrel was reinstalled and pin put back in.  I put the rifle with the pinned barrel back into the press, and pressed the barrel further in, and it now has a proper headspace.  

That being said, should I still be concerned and consider getting and installing an oversized barrel pin, or will the barrel remain in the proper position for the headspace and be good to go with the current barrel pin?

The headspace measurements were made using headspace gauges.

If it doesn't close on a field gauge, you should be fine.  I had a similar problem with a troublesome Romanian kit.  I think it was something like 20$ total for the oversize pin and reamer.  20$ was worth it for piece of mind.

What gauges are you using? What's your method?

I think you should check headspace again after test firing.
I have heard that the barrel can move slightly after shooting.