The problem with tractor paint, or straight enamel is that it will fade or oxidize.
I've used it on stuff but now have decided if I'm going to spend all that time on prep and want the shine to last I'm going to paint it with acrylic enamel.
Now I've got an old gas pump I restored and painted with Rustoleum 15 years ago. It's always outside and the paint has held up but looks pretty dull.
I used to wax it and bring back a shine, which I still could do if I had the time.
If you don't intend on letting it sit out, then the fade issue is not much to worry about, although straight enamels still don't have the gloss that acrylics will give.
Dan