It's hard to tell, but aren't the tyres old Drag Car slicks, with the scoops vulcanised on?
If so, most Common Drag tyres are 30" - 33", with the funny car and top fuelers running 36" tyres. Drag tyres are extremely light.
The Paddletyres are made from scratch, the same way as "real" tyres are, but the "shovel"tyres have "SUPER SCOOPERS" vulked on some big tyres, that might be dragtyres, they are extremely lightweighted, the compound is some kind of kevlar or something, it looks just like it's made out of an airmadras:eek13:
I'll post some pictures when i get a bit further.
For the time being, i have been collecting stuff and putting things together, so that i can(hopefully) make an easy swap, when the time comes.