Dominator made pumps with a 1" and .750" wear skirt. Sounds like your trying to put 1" parts into a .750" setup. You could purchase the proper .750" wear ring (if that is actually what the issue is) or possibly (and I'd check with your local pump guru of choice on this) cut the wear skirt down to the .750" surface that should fix your problem.
I'm sure some more knowledgable/helpful folks will post up in no time.
Chris