Ok, well, I took a 90 degree turn on this project today (been very slow going.....as in not) due to some injuries I've been nursing for a while.  Anyway, soon after I picked this up, one of our members (Jimie, who I can't @, so I guess not active anymore?) posted that his neighbor had rolled out a D6 NG Summit Platinum for free, and I scooted over to grab it.  My plan was to use that as a parts grill.  I decided this week that I would instead convert and rehab the D6, using the B4 for what parts it could offer.  So, I swapped out the NG regulator and bulkhead fittings for an LP setup, swapped orifices, and got her up and running.  All six main burners work great, with nice flame control, smoke burner works great (and looks freshly replaced), and I got the rotisserie burner working with an assist from 
@Bill Pudim.  I tried the orifice swap on the side burner, but as with the B4, I get no flame control there, so I'm thinking that a swap for an LP valve setup should do the trick.
Anyway, this grill is in very nice shape.  The flavorers are toast, but I can make use of my Dave Santana set from the B4 and a couple of the old ones until I decide a path forward there.  The problematic front panel is not pristine, but it is serviceable for now until I can figure out a plan for that.
Here she sits:
I'll break the whole thing down for a spit/polish on the stainless, and some fresh paint for the hood sides.  I've got new wheels if I decide to change those out, as well as a whole hardware set that I picked up from Weber that I was going to use on the B4 (mostly swaps over.) I'm cooking up a Tri tip tonight, and will try her out! 
R