I have a very nice almost new distributor that I was going to try out today but on trying to put it in I noticed that it's off 180 from the one in now. Can this be "changed"?

If so how?
yes all numbers match
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If you can't just pull it out a bit and rotate it 180 and push it back in, you could just move the plug wires 180 deg. and be good.

You cant do what Bob said without pulling the distributor drive gear and rotating it 180. The locating nubs on the bottom are made so the distributor only goes in one way. Someone may have removed the bottom part with two nubs that engages the drive gear and reinstalled it 180 off. I don't know that it would clear installed 180 off. The vacuum can needs clearance.

The drive on one of the distributors must have been installed 180 off during a repair or rebuild. It can be properly changed or as already stated, change wires to correspond. To confirm which dizzy is wrong, refer to Haynes or other manual for proper distributor cam gear orientation (at TDC). If you lift gear out of case to change orientation, BEWARE there is a thrust washer underneath which should be placed on gear bottom with grease upon re-installation so it does not drop off.

Are you sure it's the new one that's 180 off and not the old one?
I have a suspicion that the drive in your engine may be what's off 180.

I thought the same thing. Looking at the timing I verified that the rotor is pointing close to the mark on the distributor when #1 is at TDC. So I then have to assume it's the spare on that was rebuilt that got put back together 180 off. I also considered that I could put the wires in so that they would fire correctly timing wise for the other one but if I can pull the bottom off and have it lined up correctly that would be the better option.
Btw Bruce: that misfiring issue I've been posing about , appears to be the trigger points plate. I replaced it with the one I got from you last month and to running great. Started right up this morning too. When I pulled the plugs #2&4 were like they were brand new and #1&3 were very sooty - a big clue that only one set of points was firing properly. I thing that points plate I bought new 2 years ago might be one of those Chinese after market copies.