Two possibilities- - - -pull the rear axle and use a hydraulic press to install new lug studs, or if there's room between the axle flange and the backing plate, use a big C clamp and a deep socket, and press the new studs in without removing the axle from the housing.

DO NOT TRY TO PULL NEW STUDS IN WITH A NUT! You'll strip, or at least stretch the threads and end up in the same situation. How much torque did you use on the original studs? Most stovebolt lug studs are 7/16" diameter, and only need around 65 ft.-lbs. of torque. Most people seriously overtighten lug nuts and destroy the strength of the studs. The nuts loosen up after a few miles of driving because the stud continues to stretch.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!