Medium duty with extended/crew cab?

Hello all, I'm shopping for a medium duty flatbed and needing to stick with something that has room behind the driver's seat and/or more than three seats. I sometimes have to pick the kids up from school and need the extra space. It seems like 99.9% of medium duties are day cabs with room for nothing at all. I'm partial to older Internationals but the only option there is a crew cab which starts to make things too long. I already have the flatbed, just need the right truck. Here's the list of brands / models I'm looking for: International 4000 series Freighliner FL50, FL60, even FL70 Ford F-650 Chevrolet 4500 / 5500 (though those all seem to be automatic which is a no-go) Are there any others I should look into? I'm not sure why extra / extended / slightly roomier cabs are so rare makes no sense to me. I'd rather not do a separate sleeper (never thought they looked good except on the really big rigs). If its not obvious from the list, I don't have a ton of money for this purchase (prob $15K) so going to the dealership and ordering something off the menu is not in the cards right now. Thanks! O.