what about using the early Ranger/BII/2wd booster?
its smaller and would not boost as well, but it would save you about 2-3" in mounting depth
Camburg had mounted the master cylinder backwards next to the booster and used a teeter totter style linkage to connect the booster plunger/pedal to the master cyl
Always looked like too much work and too much going on to me
I think a F-250 hydro boost setup would also chave about 2" from your booster mounting depth, the hydro booster manifold is not as deep as our Explorer vacuum boosters are
then there is always the aftermarket/race pedal and master cylinder setups $$$$$$$$ dual master cylinders, billet, bling bling,
I want to go hydro on my BII

and on the explorer for towing, BII first since shes getting chopped up
I was looking at this the other day, and with mounting a coilover right on top of the beam (instead of on the radius arm) I think I have room to go in front of my master cylinder, the BII is running a 94 explorer booster and a 95 disc brake no frills master cylinder (same length as the brake switch master, they just didnt drill the port)