[DonC]

Depends on how granular your "specific requirements" are. If you're just talking specific power train, wheels, tires, paint color etc. there are several that can build a turnkey for you. If you're getting down to types of fasteners for the body to frame, color and gauge of wiring, type and location of fuse block etc. the selection is going to be pretty limited and very expensive.
More details about what you want would be helpful.
DonC