Hal,
:? There something that has to be cleared up here...
The sheave with the belt grove should spin freely. If it does not, take it back now.
If you are trying to turn it by the clutch plate, it should turn smoothly wit some resistance until you pull the plugs out of the rear plate. If it does not, take it back now.
It should have a tag or label indicting that it has oil for R-12 or R-134 on it Or NO OIL. R-134 oils are either PAG or Ester and they are not compatible. Don't mix them. If the pump frees up, you can empty what is in there out if you stand it on end and spin the clutch plate.
O'Reilly bought out Murry back in the O's and the Murry name was finally dropped in about 2010, so that pump has been on the shelf that long.
Were I you, I would be very cautious as you proceed.
Matt
