just drop the tank, its not that difficult and it will make fitting your T case ALOT easier.
The tank iteself will need some modifications, I removed the plastic protector completely and used a BFH to "dent" teh side of the tank so it would clear the driveshaft slip yoke assembly/cv joint. You need 1/2" clearance at least.
modifying the front gas tank bracket is a PITA, I used a 10# sledge and a concrete curb to persuade mine to clear the t case, after I ground it down a bit.
The t case is HUGE under there, but it will fit nicely if you give it enough clearance.
A new transmission mount is a good idea right now too, the 4406 will eat up your old worn out one. I plan to build a custom one with some sort of urethane bushing / mount