5/8" front spindle and 3/4" rear axle wheel swap?

Hey all. I see many of you are swapping the larger rear wheels onto the fronts. My front spindles are 5/8" but my rear axle is 3/4". I've got 8" diameter rims in the back with 20"x8x8 tires. My fronts are 6" diameter rims with 15x6x6 tires. Can I swap larger rims onto the front with the use of a 5/8" wheel bushing if they're even available? My goal is to get relatively similar size tires front and back since it's going to get a Jeep body. If I have to run 18" tires in the rear I will. Thanks, Dave.

You could use bushings to mount the rear hubs on the front. My only concern would be, if the 5/8 spindle is strong enough to use, without bending it under load.