State Farm insured my F250 before buying my 5500. I was able to convert the existing policy over to the new truck for the first year with only a slight bump up in premium but then had to go to a commercial policy due to having a GVWR over 14k lbs. This would have increased my rates by about 75% from what I was paying. I ended up with Progressive Commercial at about 25% more than I had paid before for a truck that is twice as expensive and carries twice as much as my 10 year old F250.
Reclassifying my 5500 with camper as an RV is not easy in my state and would remove some of the advantages of having a truck camper. I can consider this in the future, but then I could have just bought a Super C...