Dec 23rd Update:

Check this out!
Self-driving gift truck by 11qazxc
It's an FT based fully automated truck using a "waypoint system" by 11qazxc (using this truck, but system can easily be adapted to other vehicles), which is based on PQ-14 AI autopilot plane by rexzion. Spawn one somewhere in Wright Airport (on the ground), and it drives around collecting "gifts." Just give it a try, it's incredible.
(I'm working on an autopilot AI bomber using the waypoint system, too. Read my forum post for the general idea)

Simple ZIS-5 with M1939 37mm AAA in the bed.
Comes with a cover for concealment of the weapon. Cover gets automatically removed upon selecting the weapon.

Thanks to SyntheticL (and FOXG!) for the idea.
I wasn't gonna build this, but I had all the ingredients (M1939 was built for another project of mine, which isn't ready), so I decided to put them together. Have fun:)

Static target version of ZIS-5 truck (LINK)

Oh also, check out the XML attribute of resizable wheels. No separate shock part. I think I got a pretty good low-physics proof traction settings. Suspension is jumpy (Zero Escape anyone?) and weird though. If anyone has good settings for heavier vehicle, let me know.

slipForward
-Extremum 8 (lower this is, more grip you get)
-Aysmptote 100 (higher this is, more grip you get)
slipSideways
-Extremum 6 (same as FWD extremum)
-Asymptote 200 (again, same as FWD asym.)
traction
both 1 (=100%; apparently it's a multiplier of above values)
damper 1.5 (higher this is, less jumpy it gets (suspension will look stiffer)
spring 0.5 (if you set this too low, your vehicle will have harder time going over obstacles)

Activation code Omega
1, Null-2, 3, Null-4