Stock gears in the diffs means the t-cases have to work harder because all the gear reduction occurs there so you'll have more chance of breaking stuff in the t-case(s). Namely- input and output shafts.

Dual cases don't have to cost that much. Adapters are down to about $300 (or hold out for a used one?). A donor t-case is maybe $100 if you can't find a friend-deal. Driveshafts could be cheap/free if you do your own, or you could pay for a rear and build the front.

Just my opinion, but I would keep the built diffs. Its worth it to have both.

'97 4Runner, '06 F350, '86 4Runner, '05 WR450
http://home.4x4wire.com/erik