Have you actually gone to the dmv and checked or have you just gone to the local license office? In most states you have to go a ways up the pecking order of the particular department to get results and to get those results you have to have your end of it in order. That means a Bill of sale from the seller in Montana, receipts for major components and photos.
The thing that gets me time and time again is why the hay do you guys wait until you have several thousand dollars tied up in a truck before you even think about getting a title?
Have you talked to the state inspectors about having it inspected for a reconstructed title? I imagine you have the bill of sale from the person who sold it to you from Montana and photos of it taken when you bought it or shortly after. I also hope you have documentation on where the engine, trans and other major parts came from.
Some guys will have a hissy over the idea of a reconstructed title but that is what you actually did with the truck and according to this
http://www.bipac.net/semaga/TagTitleToolbox_MA.pdf Scroll down to reconstructed titles. You should be able to get it inspected and get a title for it.
I'd print out photos of the truck starting with the one showing it sitting in the field in montana, when you first had it in the driveway and the shots we always show on our build threads of each component sitting separate in the garage.
Get a three ring binder and a package of page savers and maybe a batch of page dividers for each section.
Start with the bill of sale and the photos of the truck as it sat.
Paperwork on the engine or a copy of the paperwork from the donor rig.
paperwork on the trans and other major components including the sales slip on the wheels and tires.
If you bought a donor rig for the engine, trans and rear and then scrapped it a copy of the title or registration and the paperwork from the scrap yard when you sold it should suffice. If you didn't get a copy of the title and the scrap yard paper notes that you had a title to give them all should be good. The main thing is that the state wants documentation that the parts were obtained legally and not stolen.
If you haven't already done so I'd pay a visit to the inspectors at one of these inspection stations
http://www.massrmv.com/rmv/titles/11salinsp.htm I would probably want to check with the local hot rodders to see which station has inspectors who are more knowledgeable about hotrods and other rigs like your truck.
Otherwise go as high up the food chain as you can at the state capitol in the main DMV office to get answers. There will be someone there who has the answer.
The other solution is to pack up and move to a state that has a simpler process.