In lieu of fancy seal insertion tools, I have purchased bronze sleeve bearings (bushings) from McMaster Carr. For instance, if the seal measures 2 5/8" OD, I buy a 2.5 OD bronze bushing from McMaster for $13. Works great and has a square face. If the bushing is a tad too big, it is a snap to turn a bit off in the lathe.

Mike in Tucson