I've got one of these kits and the tires are like yours. The tread is concave. I ordered a replacement set of tires from Carrera Slots to replace them. Very nice work so far!
Got in a Corgi Aston Martin James Bond DB5 first version. Has the changing license plates, rubber tires, etc. Needs a little love, but it's in pretty decent shape. I had one when I was about 6 and lost it. 42 years later...
Bench seats so I've got room for my buffalo butt without a center console and having actual interior room. I'd rather not have a center arm rest or center storage if it meant I had more "wiggle room"
I always find my Dremel runs too fast (yeah I know I need a speed control). So I picked up a battery powered tool from a resin kit site for about $6. It comes with bits that just plug into the end of it and it spins slowly enough that it doesn't melt plastic. It's cheaply made, but I can afford to replace it when it breaks.
Rarest I've built so far have been the Revell Lancia Stratos and the "Dr. Krook's Medicine Show". I had to make up a few parts on the Medicine Show and crib a few from the Guber Wagen, but it came out really well. I've got a full detail Chrysler Turbine that I'll be building one of these days, along with a Jo-Han Superbird.
The build is awesome! Your son should be proud. Glad I'm not the only one who remembers K&B. I bought a copy of the entire strip on disc, and also got a signed print. I still need to build Bernie's Van and Krass' coupe.