I just picked up a set of these at Tractor Supply.
http://www.tractorsupply.com/tsc/product/carry-on-trailer-weld-on-spring-seats-5-200-lb-capacityhttps://www.etrailer.com/Accessories-and-Parts/TruRyde/TRSS300.htmlOff hand, they look like they're going to work just fine. When I put them on the top of my axle, there might by 1/16 of a gap on the axle, not enough to even worry about.
They're going to get welded into place anyway.
For less than $10, not a bad purchase.
I need U-bolts and a plate still. I think I'm going cut and drill a plate and buy some u-bolts