Twinstar with engine options v1.0

Edited the truck to add motor configurations, and also increase the max speed. I didn't touch the torque-RPM scale or the max RPM, but I did adjust the max forward gear. This means instead of having an artificial speed limit, it is now limited by engine gearing and max RPM. I edited the max forward speed to match what the speed was at max RPM and max gear, it tops out around 68 mph.

I also included several engine options. I did lots of research for this. I tried to find single axle trucks and wrote down their HP and engines and then compiled a list and prices based on that. I wanted some cheaper options that are under-powered to allow myself to buy a "used" semi while I still had a smaller farm.

Model Options:
Base Paccar MX9 @ 260 hp for $43,700
Paccar MX11 @ 350 hp + $25,000
Paccar MX13 @ 445 hp + $61,300
Cummins 14.9L @ 510 hp + $98,200