Squadron has the HST M4 available again. They are not real cheap and they have to be put together, but you can finally have a ride for your 21st Long Toms...
http://www.squadron.com/ItemDetails.asp?item=HY82407
M4 High Speed Tractors
Close, but not quite...
Actually the M4 shown in the link is the one with the ammo bed on the rear for 3" and 90mm AAA guns. The one with the ammo bed for 155 guns and 8" howitzers is still out of stock. I gave up on Squander Shop and ordered mine from Great Models web store.
Gary
Gary
M4 versions...
I still haven't received my M4 155mm/8" version yet but the body isn't too different. I believe that the sides have different ventilation, there are different doors, and the "big gun" version had a collapsible jib crane to help handle the bigger ammo. General size of the ammo locker is the same.
Gary
Gary