Re: Hand-Wheel to Lever, simple switch? Things to know?
The chances of the replacement hand wheel, bolt, and spring fitting that old of a coupler are slim, while it may work it's not likely going to be 100%. Buy a hacksaw and a new coupler.
Measure the width of the tongue tubing, buy the right coupler to match. Drill the two holes needed to match the tongue. The new coupler will fit snugly up onto the trailer tongue, the forward of the two holes will end up roughly an inch from the cut edge of the tongue.
Buy good quality bolts, grade 8 is preferred and use Nylock style nuts on the bolts. When tightening the bolts down, you don't want to go so tight that it crushes the tubing or the new coupler.
If it were a galvanized trailer, then you may not want to drill into the frame, but that's not galvanized, or at least it's not any more by the looks of it. You could also take the new coupler to a welder and have them weld the new on right on. Try the local muffler shop or gas station, most have welders on hand. With the proper tools its a 15 minute job.
A lever type coupler is far safer and easier to use, those hand wheel types are a royal pain to use, and I've seen plenty of them with bad levers and springs which in turn lets them come loose on the road. I've cut dozens of them off over the years.
