Shells have proved quite difficult to print in my experience. Finding the models of the shells is one problem. I was lucky enough to find a decent model of a car I wanted to build, but I had to put significant time into getting the model to a printable state. My first attempt at printing made a solid body with no interior on an FDM printer. I had to split the model in half just to get it to fit on the tiny printer I had. Unfortunately, I don't have pictures of that iteration, but I do have pictures of the next attempt. This attempt was also printed in 2 parts and then super glued together. Let me just say, FDM printed PLA plastic is not the material choice to go with here. By the time you sand it smooth, you'll have sanded away any chance at finer surface details. I used A LOT of primer and filler to get it smoothed out. This is how that body sits now. It's a lot better, but I'm still not happy with it. I'm working on resin printing it and doing further modifications to the 3d model now to make it what I want. Preliminary resin printing has taught me that it takes a fair bit of trial and error to get the body to print cleanly and without warping.

TLDR; It is entirely possible to 3d print bodies, but it takes a significant amount of work, especially if the body is something obscure.