As far as floor pan/undercarriage color from the firewall rearward when was your car built. What product was used is typically tied to when the car was sprayed so seeking out other examples from the same plant and production period would be the place to go if there is no original color left on your car due to cleaning or blasting. Often under things like muffler brackets/hangers provides the best protected original finishes so check your car the effort will be worth it if your looking fro what was original.
Don’t recall what color mine is but it is a mid December finished example if yours is close . Also have examples from the production year that include light gray, greens, blues, a purple so batch colors as used in prior years (since 65 at least) and some red oxide examples also then the batch system had issues
My thread on details I found if they will help in some of the other areas you may be addressing during your build
https://cccforum.discoursehosting.net/t/71-cj-xr7-rebuild-warning-lots-of-pics/453/1