I bought a two body Taprite secondary reg set up. The plug nut is on the left side and the barb for CO2 in is on the right. Are these one directional or can I move the bar to the left and plug the right?
From looking at the exploded view (here), I'm pretty sure you can swap them, that's why there are versions with barbs on both sides. You could swap the low side fitting too if you needed.
The plugs are the same, and you can swap them. Note that they are in there tight and the brass is soft. Put a good 6 point box-end wrench on there, with no slip, and hope for the best. I wound up screwing mine down to my work bench to get it out.