Sorry, It was the original poster of this thread who has a 500. If your table looks like the second (510/505) or third (520) one above posted by br459 then you purchased the correct Arbor. Again, sorry for the confusion, my bad.
The first Shopsmith Manual put out by Shposmith Inc. in 1973 lists a 10" Saw Blade. Interesting though the pictures were still the original ones used from the first Mark 5 manual with an "A" Headstock Greenie. Illustrations reference a "B" Headstock. Also the Saw Blade Guard was still an optional item.
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.