Can one legally buy a "title" and use it on another vehicle.
The easiest way to answer this. No. If you go buy a truck title and never have owned the frame, cab or anything else, you could be headed for trouble. Ask yourself "what if this VIN number shows up when someone tries to register the vehicle with this VIN ?"
If you are working with a vehicle that does not have a VIN scratched into the frame, like my 46, will it be a problem if you use the frame from another truck? Probably not. For the newer trucks with a confidential VIN, you are asking for trouble. You better have the cab or something else with the VIN number...and most importantly, the paperwork to prove you own those parts. Worst case would be the parts are stolen. Right now, the street racer Hondas and whatever else are the big focus....like the V-tech engines.....lots of Hondas get stolen, show up with out the engine....Friday night at the races, an 87 Civic shows up with a nice V-tech...
Here in MN, there is a way to get a new state assigned VIN number on your vehicle. If I were spending 20,000 to 30,000 on a street rod or a frame up restore, I would take the extra time to do the VIN right too. Ask the questions BEFORE you submit your paperwork. You can probably get all the kinks worked out before you involve your truck and the VIN number....
When I bought my 46, I looked at another 46 a guy was rodding...he said it was made up of parts from 3 trucks..none of which he had the title for....he then showed me a title that he had bought...that title was not in his name either...He wanted $4,000 for the running truck....lots of good parts, fenders, a rebuilt 400....despite the "good deal", the title part was too big a risk...I passed.