Are you still planning to do all that with a 216?
I would say your goal is achievable, but you are going to need more power than a 216 could deliver. A 235 or even a 261 would help a bunch. You could use a 700r4 with 3.73- 4.11 rear gears. The 4.11 gears would probably be more desireable for towing. I wouldn't recommend any of this unless there has been substantial work done on the brakes... Disc up front would almost be mandatory.
Now for rear ends... a 54-59 chevy or gmc 1/2 ton truck should give you what you need, unless you want a posi. The ratio should be 3.90:1, however some gmcs came with 3.07:1. If you are looking for a newer rear with more gear selection, I would point you toward the IMCA modified F@#d 9 inch. You can get that rear end brand new with disc brakes in any lug configuration, and width for reasonable money. This rear end has almost an infinite number of gear ratios and posi tractions available for it. Many times it is cheaper to order this type of rear than it is to drive around to different wrecking yards with a tape measure to find a rear that will fit, only to have to completely rebuild it to make it work.
