Insurance question-classic car insurance for modified cars

[JH27N0B]

A friend of mine built a very cool custom B body.  I don't want to post pictures or too much details and possibly impose on his privacy, but it's a pro street type build with slicks on the back and no hood as the blower and induction stick up about a foot or two out of the engine compartment.
He finished the build around 4 years ago and trailers it around to shows around the country and it's won a number of awards.
He got a call Friday from his classic car insurance company telling him his insurance was canceled immediately because of features on the car making it not suitable for driving it.  It's licensed but he pretty much just drives it off and on his trailer and into show fields and cruise ins.  Illinois for all its failings at least doesn't require inspections like some states do.  Certain features on custom cars like removing the windshield wipers or having an intake partially obstructing your view might get you a ticket, but 99.9% of the time cops look the other way if they see something like that on a nice day coming or going from a car event.
He called a place or two including Hagerty yesterday and they refused to quote it.
I'm a stock resto guy so insuring my cars is not and never will be an issue.  But I see plenty of cool customs and hot rods all the time at shows and cruise ins.  Big blowers and fat rear tires mounted on narrow rear ends is certainly not uncommon in the car hobby.
They must have insurance, how and who insures them?

[Rich G.]

Try another company like Grundy or American Collectors Car. Most of them just need a few pictures. I wouldn't give them more information than what they asked for.

[JH27N0B]

American Collectors might have been the company that dropped him.  He had the insurance company for awhile and it wasn't a problem, then they called him up Friday and said they were canceling his insurance, effective immediately!  That really seems strange, he didn't make a claim or anything, so what made them do something so hasty.  If anything, if they weren't happy with something you'd think they'd drop him at renewal.
He said he talked to Hagerty and they refused to quote.  They said it was because of the fact the car was licensed but has a supercharger sticking out of the hood obstructing the view so technically isn't street legal.
I've seen lots of highly modified cars over the years at car events, many licensed, and superchargers or tunnel rams and the like are not something that rare to see.  So I was surprised to hear about somebody getting abruptly dropped for that by a collector car insurance company.

[tman]

Im sure Hagerty covers it too.  Friend had a modified 1000hp big supercharger '41 Willys and it was covered.....even covered his car coasting down the driveway and hitting the mailbox.  $10k damage.