I wouldn't fool around with a 4BT. Not enough power and torque. And not a whole lot lighter than a 6BT.

Guys put 6BTs in S10s, so it can be done.

 

Well if a 6bt will go in a s-10 it will squeeze in a c-10 or c-20!!!

Can u imagine a 6bt in a 72 swb 2wd???

 

I Have a 1991 chevy 3500 duallie, stock, 2wd, what is a rough estimate on a conversion to a 1st gen cummins motor, on my chevy.?? standard transmission, I am not mechanically inclined, so I would have to have someone do everything for me. Any suggestions, Just looking for options, thanks everyone. Zarr

 

It depends on who does it. Prices (and quality) vary a lot.

Personally, I wouldn't get anyone to do it. Even if you aren't a great mechanic, do it yourself and learn.