Proper tip sizes vary by the product you are spraying. Get a Product Data Sheet for the brand of paints, primers and clears you will be using. It will give you tip sizes, air pressures, tack times, everything you need to know for that particular product.
I've got a project planned out that will put an fj55 body on a 4 door S10 Blazer frame. I also plan to use the powertrain and do a V8 swap. Everything is readily available for the S10 V8 swap. Wheelbases are within .5 inches. I know this may upset some purists but my reasoning is sound. The fj55...