At the staging area for the 2014 Ram Truck drives, a rare specimen was on display. It was a clean, nicely-restored Ram 250 long-bed, regular-cab truck. It was familiar enough as the bodystyle of the first Cummins-powered Ram. But closer inspection showed some differences from the production-model trucks that ultimately rumbled into showrooms and started the diesel performance revolution more than two decades ago.

At first, we thought, "Oh cool an old Ram diesel." But the Ram PR staff said, "It's not just any old Ram diesel, it's THE FIRST Ram diesel." And by first, not just the first production model off the line, but the actual very first mule that was used as the validation test-bed for the Cummins B59 in a lighter-duty (i.e. non-commercial) application.

Our experience with vehicle test mules is that they're shown little mercy, and often have ample battle scars as evidence of their life of hard testing. While a dented, dinged and faded shell would have been cool in its own right, the staff of Cummins wanted to properly acknowledge and venerate the truck that put them on the map in the minds of consumers, and multiplied the company's engine volume and output almost overnight. Consequently, the truck received a full bumper-to-bumper restoration, including new paint, new interior upholstery, trim and carpeting.

Once some of the assembled media dispersed from the area, we were unexpectedly handed the keys to the truck. Knowing what a historic and symbolic vehicle this was for both Chrysler and Cummins, we graciously and thankfully accepted them. We were also given the strict orders of "no hot-rodding, and no burnouts." Just having this rare opportunity was enough for us.

We started up the 12-valve 5.9-liter inline-six, and were immediately reminded of how far diesel refinement has come in the past two decades. The purely mechanical diesel sent a persistent and unapologetic shudder and buzz through the chassis and body. Stopped and in-gear, the rearview mirror is practically useless for the amount of vibration made by the engine. A little bit of throttle smooths out the power pulses enough were you have decent rear visibility, but the Magic Fingers sensation is never far removed.

The original 12-valve B59 was built before the days of electronic fuel injection, and certainly well before the clatter-cutting "pilot injection" technology was implemented. It's a diesel's diesel, feeling every bit the scaled-down Class-8 engine it was in many respects.

Since there was no tachometer on the mule, we can only guess how fast we were turning over the engine, but at no point during our drive do we think we exceeded 2000 rpm. The three-speed TorqueFlite seemed to insistently downshift at the slightest application of throttle. The redline for the old 12-valve is somewhere in the neighborhood of 2500 rpm, barely above the redline of most Class 8 engines.

Thankfully, we returned the truck to the staging area unscathed, thankful to be entrusted with the granddaddy of modern diesel pickups, the one truck that can be credited with starting the modern diesel performance revolution.