I replaced the small wheels with large Princess Auto surplus wheels I had in stock. The idea being to keep the spreader gearbox from overloading at the higher tow speeds. The coverage will remain the same by opening the feed gate wider.
I removed the push handle and replaced it with a bent piece of tubing to keep the frame solid. The tow frame was bent up from 1 1/2" by 1/8" strap steel and bolted to the frame in 4 places to keep everything rigid. 2-5/16" shackles completes the tow hitch.
The spreader works great and will take 50 lb. of seed or fertilizer and criss crossing 6-7 acres took an afternoon as opposed to days. Got almost done this springs application today, till storm clouds rolled in. Here's a picture I took last year.