if you want to jump on the parts, these have 1" diameter axles--isn't any way you're going to get stronger than that unless you go automotive. SAE fasteners, SAE common bearings in the hubs, 4x4 bolt pattern and 8" golf cart stock rims are dirt cheap and there are larger size options and many styles on the market because of the golf cart modders. All you would need is to fab up 4 a-arms and revise the steering arm lengths and mount holes to match your steering rack.
By the time you do a hub and spindle set up alone, unless you're finding free atvs, you won't get something as dependable = worry free for even 2x the price.
http://www.ebay.com/itm/Used-Golf-Ca...item484556b1b1