Sounds like you car is a perfect candidate minus turbo for the THS class. I would consider THS more of a street class than any other class out there with their high car count and looking at the cars myself. Even TSO has the word STREET in it. I would place XTSM as a middle class between street car and racecar. TSO would be considered an all out racecar class with basically anything goes. This leaves virtually everyone a place to race. Based on the wipers, horns, and lights that you are asking about, this may not be the class for you.
I have really no dog in this fight I will state. All I want to see is increased car count and participation and as a race director at 2 Buick events, I can see with current car counts that hanging on to things that once worked in the past, may not be the best way to stay for the future of Buick racing with the exception of THS. Im still fighting Index racing but thats a totally different thing all together