I have been asked “What is the weight of a Model 10?” It is hard to say since revisions made to the parts from 1947 to 1953 also changed the weight. Several parts had their mass reduced such as the Base Plate. Others changed to lighter materials like Aluminum vs. Cast Iron as was done with the Headrest and the weight changed from 14 to 7 pounds in the parts lists. Way Tubes had their weight reduced by almost half when they were changed from 1/4” to 1/8” thick walls. It is safe to say a basic Model 10E from 1947 is heavier than a basic 1953 10ER. The Montgomery Ward catalog around 1949 - 1950 with a later 10E (metal extension table) lists the weight with a motor as 205 pounds. The ½ HP motor is listed as 35 pounds. That weight includes the original accessories (sanding disk, arbors, fence, etc.) included when purchasing the basic unit. Now add the weight of the bench plus caster assemblies and anything else that is on the bench when moving. 75 pound rated casters may be able to handle it but I believe they will wear out quickly. I would recommend a higher rated castor.
As for the length of the castor's mounting shaft, it is important for the original style castors since they "ride" on the end of the shaft. Ball bearing swivel castors can have the sleeve riding on the top of the ball bearing swivels plate so the shaft can be shorter.
One more thing to consider is the height of the castor from the floor to the top of the ball bearing's swivel plate compared to the original castors. if it is different you will have to drill new holes in the bench ends to adjust the height of the castor assembly.
Mark V 520 S/N 09-11-01 completely upgraded to Mark 7, with all SPT's & more.
Model 10ER S/N R64000 first one I restored on bench w/ Shopsmith metal ends & retractable casters. Has Speed Changer, Model 4E Jointer, Jig Saw with lamp, a complete set of original accessories & much more.
Model 10E S/N 1077 oldest one I have restored. On bench w/ Shopsmith metal ends & retractable casters.