Are you talking about Dayton type wheels when you say "spoke"???
As for the parking brake arrangement, the transmission might not be the original. I very doubt the builder would have use a setup like this one for a fire truck. The chance of forgetting the parking brake activated while engaging the pump causing the truck to stall and not restarting or smoking the park brake is too great, plus the fact that you are loosing park brake with the pump engaged. Do you have an other park brake system at the rear wheels?
I've seen fire truck with both, single or two speed rear end.
It safe to say about half of the milage is actual road miles, maybe less.
J. F.
