So, I did some research...this may be one of the most unique Commanders still in one piece.
Yes, it has a STOL kit. It was the experimental testbed for the Robertson STOL kit on the 500 series. It used a modified kit that was originally approved for a 680E. It was in and out of experimental status several times for the STOL kit evaluation. I think only one 680E was ever converted and only one 500B was ever converted. It looks to me like it's out of experimental and the kit is still on, so that makes it one of a kind right there.
It had a massive amount of radio gear installed at one point - 380 lbs worth. It was on several racks in the baggage compartment. It included two ADFs & rotating loops and an HF radio with an antenna on a reel.
The baggage compartment was extended (see photos)
Yes, the engines are TIOs - it had a Rajay kit installed.
Yes, that's a fat nosewheel - it's a 7.00x6 at 28 psi. The nose strut was raised an inch.
It had the McMillan radar nose with an RCA radar.
It's one of the fatter 500B's I've seen - it was 5100 lbs BEFORE the Rajays and Robertson STOL were added. The radio racks were removed a few years later when the baggage compartment was extended.
It went through over 20 owners. It was in air taxi in Alaska for a short while, but it was mostly corporate transport.
I don't think you could resurrect it for $100k. Two engine overhauls & turbo overhauls gets you up to $150k before you've even had breakfast. And you can't overhaul the props - there are none.