You can find older trucks with newer drive lines. Here is one I did and sold. Into the high 12's with those big tires.
The only thing a big block has over a Cummins is the Kerchunk-kerchunk. And it is able to drink more and get less out of it.
These are pics of the same truck. I tried big blocks also. Nothing ran like that cummins. The truck was unbelievable fast and ate alot of mustangs on the street. Couldn't do it with the 8's even with the blower. They had no torque on the bottom.
