Hard to say. Looks like the only engines available from the factory for the 1969-1970 model year for the L700 were Dodge gasoline engines:
http://www.olddodges.com/index1.htm
Knowing the Tommy Ivo truck, it's highly modified.
Looks awesome, Charles. Fantastic weathering job. What do the numbers (90, 80, 60) on the rear of the cab signify? I've seen these on European trucks, and I've always wondered.