Matt,

Is their going to be more than one manual tranny option too? Personally I would like to see one of the spicer/fuller/eaton 7 or 9 spd tranny's with a low gear in the 8 or 10-1 range, with preferably an O/D, but if a tall enough axle gear is availible, like 3.73's, a direct drive tranny would work too.
On the other hand an allison 3060 tranny would work too, a better load moving lower overall first gear than the 1000 series.
I'd like an over all low ratio such that I can pull about 30K up a 35% grade, and still have the engine turning about 18-1900 rpms at 60-65 mph.
Bed size, I'm thinking 10' with very little overhang of the spring hangers, about a 72" CA IIRC for that spec. I pull a trailer with a pintle hitch, and need that hitch to be as close to the axle as I can for the best handling.
Top speed is not a key thing for me, it's "not getting stalled" on the 20-30% grade driveways I move my equipment trailer into yeards that I landscape here in the NW.