just an update.
1. Hagerty insurance will only insure 1984 and earlier M939 series trucks now, they require the truck be stored inside, NO off-road use and no camping in it! if you want to insure it as an antique.
2. the Ma. RMV is going to try to get you to attach an assigned VIN plate to your truck if it is after 1981. If your truck is 25 yrs old. but later than 1981. Tell them it is a Antique military truck and you want to keep it original. they will put your truck in as a 1981, then call the help line and have it changed back to the proper year. A few of my friends and I have done this.