Those threads inside the hub are for a puller, but using a puller may not be needed on an old mainshaft and a 57 year old clutch. My AMC clutch (same as yours) slid on and off by hand. Crank down the nut to 60lb ft of torque. It'll take 70, but between 60 and 70 works. The Commando clutch can't take the higher torque against the circlip. The Atlas clutch butts up against the outside step face before the splines on the mainshaft start and can take higher torque. A certain someone will say it can't take that much torque and you'll bend or break the mainshaft, but not true. Get the clutch locking tool. It'll make torquing that nut down much easier.