Try these- - - - -you'll need to fabricate something like a 4-link system to position the axle, but the weight capacity looks right.

www.ebay.com/itm/121872996666?

OOPS! That one's got independent suspension, not a straight axle! Just fabricate upper and lower supports to substitute the air bags for the coil springs. You might need to adapt to an outboard shock absorber if it's through the center of the spring.
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!