When I removed my body I ran 4X4's along the length and bolted them down through the body/frame holes. This gave me rails I could jack under and move around without messing up the bottom edges of the body. I was lucky and had access to a fork lift. I made extensions for the forks and moved the body easily. When it came time to sandblast I was able to lift it on to tall jacks and walk under it to blast and paint. I blasted everthing including a light blast on the wood. I primed the steel under the body with an etching primer and a urathane primer, then painted with an industrial black enamel. I didn't worry about over spray of the primer on the wood and painted the wood under the body with the same industrial enamel.
Taking the body off the frame is really no big deal as long as you consider what you are going to do with it and how you are going to move it around once it's off. You may spend more time and engineeering building a dolly or some other device to make you work more successful.
While mine was all apart I figured I would go ahead and install a Heidts IFS Mustang II with a manual rack and pinion. I am building a daily driver.
You mentioned your gas tank straps being screwed into the wood. I don't know if that was the way it was done on some trucks or not but it sure seems dangerous having all that gasoline and weight suspended by a couple of 5/8" wood screws. Mine bolts into two steel cross members. I would recommend getting the factory fabrication manual for these trucks. It has been very helpful to me on this rebuild.

All the best, Ted