That 400 in there is an awesome motor. It will absolutely haul ***** with some low dollar mods. The 60's are about as tough as they come as far as diff's go. I have a real soft spot in my heart for the '79 body style. when I was in my early 20's I rebuilt a rolled shortbox 4x4. It was the ultimate beach cruising, mud bogging, Mustang eating 4x4! I only wish we had video cameras back then! Definitely some Youtube-able stunts were performed!
Pro's: lots of them around for chassis parts. Easy to build and maintain.
Con's: the 60 front is very desirable for off road projects which makes some of the parts hard to find. The camper body will be next to impossible to find replica parts for. Anything that needs to be replaced may need to be re engineered as well.
Good luck with the purchase! That's such an awesome find!