As Walt stated the smaller filter is one to use. That's what is used on my 2002 ISC-350.
In regards to the Coolant Shut-Off Valve, the safest way to turn it off is to do it when you change the oil and oil filter.
With the oil filter removed and using a long handled needle nose pliers or some other device, grab the end of the valve facing the oil filter housing and gently work it back and forth gingerly until it is free enough to turn it 90 degrees to off.
If you attempt to turn the other end with it seized trust me it WILL break.
With the older engine that you have they just may have a SS version of the Coolant Shut-Off Valve to replace the plastic valve. You would have to ask the Cummins Dealer plus have your engine serial number when you go.
See these TWO threads regarding the Coolant Shut-Off Valve for additional information.
http://www.irv2.com/forums/f123/what...re-136370.html
http://www.irv2.com/forums/f115/2000...er-281144.html
Dr4Film ----- Richard