Just make sure your front axle is strong enough to take the abuse of whoops and landing from air time with the front locked. In our jeepspeed car, we had a detroit in the front, spool in rear, always run 4wd, and it exploded a coulpe D44 chromo stub shafts. We then ran some sort of Posi unit, and we liked the way that worked the best (it was a stock 9 inch posi, I believe, and it sheared the ring gear flange off the carrier. So we threw in an open carrier, and it has been dependable ever since.
I would think if you ran a spool in the front, you would really want full hydro steering, a good fluid cooler, and an axle wit BIG ball joints.
Richard is dead on with it pulling through corners rather than pushing, and it's a lot harder to get a drift going.
-Dan