Those shotup trucks in Tucson, AZ were probably used for target practice in training activities. Trucks, or any equipment in general, that was not serviceable was not returned to the US. They were collected in scrap yards and who knows what happened after that.
In Viet Nam damaged Huey helicopters were broken down and the central portion that included engines and the transmission were brought back on aircraft that would otherwise be dead-heading back. The scrap yard at Ben Hoa was incredible, an MV lovers wet dream. We needed a transmission for an M37 and wound up getting a whole truck that had a blown engine. The ‘parts truck’ was better than the one we were trying to repair.
As far as I have been able to confirm, the only equipment that has come back from either Viet Nam or Iraq was equipment that belonged to National Guard units because the ownership is technically different. I believe that Federal units, including Army Reserve and Regular Army units, did not bring back anything other than critical equipment. In the case of Viet Nam, a lot of equipment was given to ARVN units when we pulled out.
I recently acquired an M109A3 deuce with a box which was manufactured in 1966. I know that the last unit to own it was the 39th Inf. Bde. that served on the Syrian border from 2004 to 2005. The 39th Inf. Bde. Is a National Guard unit from Arkansas and they apparently brought their equipment back with them. My truck had customs papers from Iraq still taped inside the hut. There is a decal with their patch, a Bowie knife, on the driver’s windshield. See
http://www.steelsoldiers.com/index.php?name=PNphpBB2&file=viewtopic&p=144726&highlight=#144726
It’s just supposition, but it appears that the same thing happened in Viet Nam with this truck. The 39th was re-equipped in 1967 and deployed to Viet Nam in 1968 as part of the 4th Inf. Div. The 4th came back in Dec., 1970 so this truck probably served in Viet Nam and in Iraq.
A Steel Soldiers member that might be able to cast light on this subject is ARMYMAN30YearsPlus. He has had personal experience with some of this.