Hi Bean. Your car looks nice in the photos I've seen. The person you bought it from bought it from a gent in Saint-Sauveur, Quebec on 18 April this year. He is the same guy that owned it in Florida. I guess you bought it from Woodbridge on 30 June.
Your seller flipped the Cobra for a quick and tidy profit, so I wouldn't expect him to have much interest in the history of the car. If you haven't done so already, you could contact the long term owner here;
4mydakar on eBay
He's the guy who would have done the rebuild 15 years ago, so should be your best bet for vehicle specs.
Don't feel obliged to remove the Chevy engine. Lots of Arntz and Butler Cobras were Chevy powered, including mine