Overhaul kits for the Detroit Diesel Series 60 run from $2300 - $5000 depending on what version of the engine you have (the 14 Liter EGR engines are more expensive). A good place to start would be to give
Diesel Rebuild Kits a call them a call with your engine serial # so they can properly identify all of the correct parts for your engine (there is some variation among these engines so you always want to be sure of what your working with).
A good place to start is here:
Detroit Diesel Series 60 Engine Kits & Parts