Or, you can do a Priest, Hellcat, or Jackson., . These have open interiors which would keep you form having to cut the hulls of standard tanks or not being able to see much of the interior.
I was going to suggest the 113 track but the others beat me to it.
Another consideration would be the Hobbyboss Vietnam armored car they call the M-706. It's a Army V-100 M.P. vehicle but has a interior with the parts for the machinegun turret. All you have to do is leave the hatches open and add a few details to them. I've got one that I'm getting ready to convert into the Air Force M-706 Commando Car.
Just something to think about.