My car had been sitting since 1981 and I have changed all the fuel and vacuum lines, cleaned the fuel tank and flushed those lines and I just got back my injectors from being cleaned.

All that being said do I need to purchase a new Fuel Pressure Regulator or is there a way to clean it or would it not be an issue?

Never seen one fail. I have 2 or 3 and I have interchanged them and they all work. I have a FP gauge in line and it looks good to go... Try it.

I just didn't know if old gas can sit in there and ruin it or if you needed to service/clean it. If not then I will just leave it alone and cross my fingers.

Wouldn't hurt to take it out, tap it on a towel and see if any debree comes out. If not, shouldn't be an issue. Could probally even squirt some brake cleaner in it to clean out any residue.