Okay, so here is another model. The colour code is included in my screenshot, windspeed of 25m/s applied (56mph which is the UK speed limit for a truck of this size).
Truck is 15.1m long, 5.1m from top to bottom. The car is 3.7m long. The distance from the rear of the truck to the front of the car is 54.0m as requested.
Seems to me that there's no slipstreaming/drafting effect at this distance. Clicking the picture will open up a 1920x1080 version.
