Insuring your vintage camper is probably a good idea, but not required by most states.  I have heard from many people that a lot of insurance companies will not insure a vintage camper.  But, if you check around you can find an insurance company that will insure your vintage camper. The price may be high, but checking different companies, you can get a reasonable rate with good coverage,  Below is from David :

Insuring your Scotty for a fair value from David Turner:  "We have our Scotty insured through Foremost insurance, which is an AARP insurance group (1-800-237-2060) at a rate of $100.62 per year.  We have the following:

$ 5000.00 on the Scotty - will need to provide pictures.
$ 250.00 deductible
$ 2000.00 personal belongings coverage.
$ 50,000 liability insurance, even on camp ground.
$ 10,000 act. death.
Towing and road side service even for the tow vehicle.
This covers wind, fire, etc.

You can check with other companies and see what you can get. (August 2006)

UPDATED -  MARCH 1, 2008 from David Turner:

"we have Foremost insurance for all 3 of our campers, it runs us about 300 per year , what it covers is, the camper of coarse, replacement value, ours are set at 5000 each, (what you do is send them pictures and tell them what it would cost to replace them, and we were approved for 5000 on each, ) it is covered setting in the driveway, on the road, and at the campground,  it also covers liability at the campground , say if someone would get hurt, because of something on your site, or camper your covered, it also covers content up to 2500. and road side service,  if i get a flat i call them they send someone to fix it , of coarse i might be there for a couple of days waiting but its covered.