Thanks for the rear cargo area info, seems similar to a 54.
The flat tire, oh yes, I had to factor all of that into my build as well.
http://67-72chevytrucks.com/vboard/s...4&postcount=49
I ended up building my coilover mounts for as long of a coilover as I could get away with, and setting it up for more droop travel than up travel so I could get the tire off on the side of the road without unhooking suspension. After some testing, it worked on my application!