5" Front Drop + 28" Tire = ???

[TIMSPEED]

Anyone think I can get away with 5" of drop in the front and still run my 28" tires? I have 255/55 17's up front currently, that from the factory (Kumho) are rated at 28" tall. I think with the weight in the front of the truck the tires measure out to something like 27½". Currently I'm running 3" DJM Drop Spindles, and my drivers side measured up to 30¼", and my passenger side measured up to 29½". I think two things are going on here...
1.) Sagging stock front springs
2.) Sagging body/cab mounts.

So, if I replace my cab/body mounts with brand new PST ones, and then swapped in a set of either 1½" or 2" springs, would it work out and not rub?
BTW: I have hedman headers on the truck now, and the very BOTTOM of the collector FLANGE is exactly 6" off the ground...I wouldn't mind if it was only 4" off the ground, since the bottom of my collector flange in my VETTE is 3" off the ground and I NEVER have ANY problems with that...