The good thing about Willys, you can take the best parts, and combine them together. One never knows exactly what you have until you tear it apart and examine all the parts. A CJ3A tub has slightly more room for the driver and passenger, with the wheel wells set back further. The windshield is taller, and one piece. Some of the early foreign made bodies were a hodge podge of parts. The pictures below are of a early MD Juan M38 body and frame, compared to an original M38. The only real difference is that there is no provision for an in cowl mounted battery box. The quality of the steel used for the tub was crap too. The replica Jeep did spend it's life in the rust belt, but it was only driven during fair weather. It shouldn't be that rusty.
What size Cat is in his CJ5? The only small engines that are branded Cat are actually Perkins.... Perkipillar if you will. Good little engines. I keep thinking that for what ever reason, I would be up to putting in a Detroit 4-71 two stroke screamer.
Your jeep looks like it turned out pretty well. I don’t think I could tell the difference between a replica and an original. I bought this CJ3A thinking it was an original CJ3. I am a little better educated these days but I have a long way to go.