I run a similar setup with a center dif in a G2R chassis and the truggy ratio f/r diffs are the way to go IMO. It lets you run a standard 46T center dif and still be able to gear it reasonably. The buggy difs with the 46T center and truck tires forces you to go down to tiny little pinions which increase wear on the pinion and spur IMO and have a tendancy to break the platic teeeth on the spur also when the pinion is that small.
You got the right plan going and I love the truck. Looks sweet and a very slick setup. Cant wait to hear how it goes for you. I love mine.
BTW heres a couple pics of mine in case you are interested. These pictures are a little old, I'm running a different motor and speed controll setup now, but it is still the same concept and basic layout.
