I plan on doing mine with PPG's Delfleet, which is similar to Dupont's Imron, polyurathane. A very strong and durable paint that is used on semi-tractors. I have use this several times before in the past doing autobody repair and paint. There is several different brands and product lines to choose from. I am partial to PPG having use it for 20 plus years. Mine is a wood body and I plan on stripping all the paint to be sure the wood is in good condition. If you are working with steel, I would go by the condition of the paint and body. If the paint and bodyfiller are not cracked, you can get a very nice finish just sanding it putting primer-surfacer on the places where it is needed, then spray a new paint job right over the top.
If you have any questions I will try to answer them.