I think the bottom line, though, is that it all depends on the condition of the vehicle (is it restored? A well-preserved original in pristine condition? A beater or well-worn original pulled from the barn and still struggling on?), your intended use of the vehicle (occasional pleasure use? Limited work? Daily driver? Trailered to and from shows?), and (most importantly) your record.
Rarely will any two of us get similar quotes. And neither can you expect to get low premiums if you are in a high risk group or your truck is a daily driver.
Most of the specialty insurers base their low rates on insuring "good risks" -- guys who don't use the vehicle very much and are likely to be very careful when they do. Their research tells them that people with hoopty mobiles tend to be less of a "good Risk" than people with well-maintained show vehicles. Obviously, your individual case may vary, but that's what the over all research shows the insurance companies. Read the Tech Tip mentioned above -- it explains all this.
As for me, I use three different insurance companies -- GEICO for our daily drivers (and I've had nothing but fantastic service from GEICO -- They've been great to us and our teen-aged drivers

), Hagerty for the '49 and Gulfway for the Big Truck. Gulfway is a little more expensive than Hagerty, but they have less restictions on the big truck. (Hagerty didn't want me pulling a trailer, for one thing ... um, it's a semi tractor ..

Insurance is a pain, but part of the overall fun

John