Just to be sure we're all on the same page.

Gen I SWB Trucks:
A/T Oil - Two in series coolers. One inside the radiator. One air cooled radiator.
M/T Oil - N/A.
Engine Oil - None.

Gen I LWB Trucks:
A/T Oil - Two in series coolers. One inside the radiator. One air cooled radiator.
M/T Oil - N/A.
Engine Oil - One air cooled radiator.

The engine oil cooler found on the LWB trucks can be installed on the SWB trucks. The SWB oil pump has the radiator inlet and outlet ports blocked off with plugs. Be sure to get all the hose mounting hardware and brackets. The only modification needed to the SWB truck is to weld on a hanger for the hose bracket where the hoses pass through the radiator support.