It takes a special perch bolt that will accomodate the swivel and the shock arm - somewhat hard to come by but I do happen to have a set if you are interested - PM me if so.
How you tell the perch bolts apart is by the shock mount (there are numbers on them but I never can remember one from the other) - it should be fairly obvious that way.
More photos that may help. Please excuse my "Charles Atlas" muscular arm and Gucci shirt sleeve. As you can see the perch bolt also accomodates the shock mount and the stabilizer.
Enclosed are some pictures of a '40 swaybar on have on my '35. There are a lot of after-market swaybars on the market but you can't beat a '40-'41 for the "factory look."