On the road, I'd say leave the front tranny in 4th (1:1) and shift the rear tranny. I would think there would be less ware in the system that way. The idea of being able to do it is cool but the fact that toy trannies gearing is pretty high in first gear doesn't make it a viable solution in my mind. Tons of gears to choose from is cool but really you can get more overall gearing out of triple cases and still be shorter.
I've seen a few people do dual trannies using sm465s. That would be a cool setup because you can run a bulletproof 205 behind it and even with the 1.92:1 gear in the 205, the 6.55:1 gears in the trannnies would still put you at or above 350:1.
