The Chevrolet Colorado is an good platform IMO and keeps it on the small. On the large-end I would consider a Dodge 2500 with Cummins diesel, purely for the Cummins and manual transmission option.
I like the looks and moderate body size of the GM HD2500s, but don't like the idea of only automatic transmission and a mostly/reasonably unmodifiable front suspension system.
I might even say Ford Ranger. The running gear appears from a distance to have some faults but I hear very few things wrong with these little trucks?
I've seriously considered selling some Cruisers and doing a full-size domestic build, but they're just as spendy as a new Cruiser and I don't like bench seats.
UZJ100 "Mama Kuiser" built to look cool for the soccer mom
FZJ80 über rare "Geen", cloth'd & locked