Back to my search for the perfect solution, I'll expand a bit on my plan as I am really unsure of my next move.
First thing is, I'm very happy with the setup of my truck right now (sits level) aside from the darty steering caused by no caster correction and the 851's plus 1.5" spacers. It is plenty tall to clear the 315's and it performs exceptionally offroad.
Second is that I just ordered a big heavy front winch bumper and a Dual Swing Rear with Spare and 11.5 gallon fuel transfer tank from DC Fabrication. The spare will always be on and the tank will be full 90% of the time. Once the spare is removed from rear cargo I will be putting a fridge and OBA in its place.
In short the Medium lift will no longer be sufficient. I need some help. I want to achieve a overall height about the same or a tad taller than current and fix the caster all at the same time. My first thought was to go heavy front and rear, leave the spacer up front order plates and be done. But after looking over many spring, caster, drive line vibe/DC Threads...

I'm thinking I would be better off with J's due to likely not needing the DC Shaft because of:
A. All the Weight so it wont be as tall as a lot of these other trucks running around with this setup
B. Barely getting enough caster adjustment with the plates to compensate for J's and the spacer thus keeping pinion angled up towards T.C.
C. I'm feeling lucky
Another option obviously would be J's (ditch the spacer) and Heavy rear. If its too low or caster adjusted too much with plates causing vibes I could always throw the spacer back in and trim packer the rear to level?
What do all the heavy haulers think?
Get the weight on it then decide?
Get the plates on now, then the weight (to see if it negatively affects drive vibes or steering feel)?
Knock over a Kwik E Mart and order the Slee kit...

no money for that.
Normally I would just trial and error but time is at a premium and I have to be ready for 5k mile expedition in June, so a guaranteed solution that doesn't involve a DC driveshaft would be ideal. ( I know, I'm cheap and broke due to a wedding so I'll do nearly anything to avoid that added expense since I'm already dropping over 6 Grand in upgrades over the next 3 months)