How ta tell
tateinca,
It's all in the fuel pump. Open the hood, on the right side of the engine, as you stand facing the rear of the truck, is the fuel pump. 1st Gens have the VE pump. The fuel lines come out the back of the pump through the valve covers and to the injectors on the left side. The 2nd Gens have the P7100 pump. The fuel lines come out of the top in a straight row, then head through the covers etc.
I have not read or seen a "2nd Gen" engine in a 1st Gen truck. My guess on the VIN is the eigth digit "C" stands for a diesel engine in general. Tell us what you find.
Art