I've been with State Farm as long as I have been driving. I tried one of the 'collector' companies for the Corvettes a few years ago, but came back to State Farm because the collector programs seemed to restrictive. SF sort of has a collector/exotic program although it is admittedly not as inexpensive as companies like Haggerty. But, through State Farm, I can drop collision and liability when I'm not driving the car, leaving only comprehensive while it is in storage.
All of the "collector" insurance companies I looked into require either that you carry full coverage for the entire year or not at all (meaning you can never drive it). For me, being able to have full coverage only when I'm driving the car works out to be cheaper than carrying full coverage year-round through a collector company.
For the Speedster, and for the L88 I recently sold, SF required me to get an appraisal for an 'agreed upon' coverage amount since it was higher than a standard Corvette of similar vintage. They had never heard of a Callaway Speedster before, but they agreed to insure it for the full amount.
I did check with Haggerty again when I got the Speedster and found it interesting that they wanted to put it in their "exotic" program. I found it interesting that the price through Haggerty for comprehensive only (never driving it) was about twice what State Farm quoted me, and with State Farm I can call my agent and put full coverage back on for a short period. Haggerty would not allow that, so in this case SF came out WAY cheaper than Haggerty.