Don't do it.

At least I don't recommend it; especially if you're ever going to tow anything. In my opinion, rear drums are fantastic for stopping power versus discs. Discs on the front are ok; but you really don't want discs all around if it's ever to be towing anything.

Just my experience in having owned 2 nearly identical SUV's - one having 4-wheel discs, the other front disc, rear drum.

The latter has only required one set of new brakes in 115K miles; the 4-wheel disc truck went through at least 4-5 sets of brakes in 150K miles. Both trucks towed the toys on and off, and I felt loads more comfortable in stopping ability with the rear drums.