Couple of questions

1) Ive heard that if I flatbed my F250 that Im going to need to get commercial plates? Any truth to this?

2) The cab im putting on has a different VIN number than my truck, so what do I do? I could swap the vins from the old cab onto the new one, or?

#1 Nothing has changed on your truck other then the Bed Depending on your state laws as long as your not exceding your maximum allowed GVRW
Here in Ont if we go over 4500kg (9920 lbs we need a commercial registration and an annual inspection.

#2 Again depending on your state law. If your chassis and cab are not original to each other, they both need to be registered on the ownership. Some states only require just the cab registration VIN.
As the situation with my 57 chev I will be switching out the chassis, Ownership won't change, cause the cab's VIN is still intack.

Hope this helps. You still need to go to your licensing office to ask questions.

On top of what Glenn said;

1) as long as your flatbed isnt any wider then the original width of the truck, no.

2) You'd need to reregister the truck with the new vin, easy way out, swap vin tags.

OK well im gonna swap the vin tags i guess instead of dealing with a bunch of BS. Might as well keep it easy lol