There are a few differences between the two cars.
Tire size is one of the easiest to notice differences. His has trailer tires, which are pretty close in size and shape to what these cars originally came with.
Mine has a funky 13" wheel and tires, but they are actual radials. Supposedly, they ride much better.
I really don't think that the difference in tires is a huge difference.
Besides, a battery charge isn't like a tank of gas. You can't just run it until you stop! That's really hard on the batteries.
Rich's car has more lbs of lead in it. Part of that is the battery tray under his seat is larger, and a nice, rectangular shape. My tray is an odd shape because the motor sticks in, at a right angle to the rear axle. His is parallel to the axle.
Here's what it looks like under my seat.
Notice how the motor intrudes on the battery space. I DO however have a higher system voltage than Rich's car. Mine currently runs at 60V and his is 48. That means mine goes faster! Also, it pulls fewer amps to do the same work, because of the higher voltage.
I am trying to figure out how to fit one more battery under the seat. The motor is off-center, and the batteries are not the size that the vehicle was designed for.
It looks like it may be possible to remove the speedometer cable from the end of the motor and then line up six batteries in there.
I'll put that on my list of future modifications...