yes, for sure check the driveshaft clearance at full jounce of the suspension.
I have used a length of abs plumbing pipe or a piece of 1x4 board on edge to simulate the o/d of the driveshaft as a quick reference to connect the dots between the trans and the diff. depending on the o/d of the pinion and the trans output housing a large piece of abs could slip over those parts. a piece of fence board can be cut to capture both ends and be held in place with tape for all the time it takes. not so much work as finding and bolting on the d/shaft.
haven't seen a good pic of the rad area but maybe, for the battery, out in front of the rad, down low so as not to restrict air flow? move muffler forward/back to allow a little more room in that area, with a heat shield or 2? moving back further would require larger supply cables but. really, lots of big trucks and heavy equipment have their batteries located quite a distance from the engine bay/alt/starter. their load draw would be considerably more. battery at the rear would mean lots more space, probably, and easier access. maybe a battery tray on a leverage system, like those old fashioned lamps have, could work to take the load off the shoulders in a service environment. if you make the tray the right size a lid from something else, like big rig, farm tractor, small equipment etc, could work to cover it up. or possibly a marine battery box (with a vent) or if you have the room a sliding tray like an rv would have. I assume the truck box will have a raised floor so there could be room under that behind the axle (more chance of the battery getting shook around back there though)? depending on the look you are going for possibly an old cooler or tool box in the bed could be used to hide the battery, provide some security (lockable) and also look cool.
here is a few links. some have pics/ideas from this site.
http://67-72chevytrucks.com/vboard/s...d.php?t=215890
https://www.amazon.com/EZ-GLIDE-BT07...DQ9VGV3MRQ0NNS
https://www.summitracing.com/parts/a...BoCtpMQAvD_BwE
https://www.boatownersworld.ca/DUAL-...rs_p_2959.html