The VINs won't be an issue. Too easy to buy a rust bucket junker just to get the vin and whatever parts can be salvaged and reused / repaired
Then it's not a "new" vehicle. It's repairing an old one
In a lot of states you don't need a title on old cars anyway Just a bill of sale
Seriously people, be careful giving or taking this advice.
You cannot legally change, modify, remove or replace (with a different VIN) the VIN on a vehicle. It's debateable if the VIN goes with the body, frame or pair. It is very easy to do on a Bronco due to the VIN tag being on a removeable part, but that doesn't make it legal, it is VERY Gray, you aren't changing or modifying the vin plate, but you are moving it from one vehicle to another. There is also at least one VIN on the frame.
It's not impossible to get a new VIN plate from the state for a replacement tub, people do it all the time for street rods and kit cars.
If you built a Bronco using a Krawlers Edge or simiar frame, and a Dynacorn or Fiberglass tub, and added the VIN from a real Bronco, you can go to jail. All it takes is a tag agent to get a bug up their rear and force you to get a frame inspection by an LEO before issuing registration or for an auction house, professional appraiser, or insurance adjuster to look at it. It is a felony. I have seen people go to jail for changing the VIN and the new owners filing a complaint.
Even if a title is not required by the state the vehicle is sold in, it very well may be required by the next state it is registered in. Do your homework, if there is any question consult an attorney.
As a licensed, bonded dealer that gets paid as a consultant to look at this type of thing, my advice is do not try and pull the glovebox door / title trick to get a vehicle to pass registration. If we can't verify the VIN on the body matches the frame (even if its just worn or rusted away) we will not appraise, sell, buy, consign, or represent it.
[/rant] back on topic.