Hi let me look at question carefully and I'll be rite back
I have been doing this for 30 years and never seen one yet and I do look at a lot of books aftermarket and Cummins.
That being said I have seen aftermarket electric tachs that can be hooked up to your engine with a little work The crank turns one to one [of course I know ] and the accessory drive turns at 1/2 off engine speed the electric tachs you can find at speed shops or magazines so you would be able to hook up to read of off the crank or accessory drive pully if you read off of ass.drive you would just put 2 tabs of electric pick up tape 180 deg apart so it would count 2 and then that would be equal to rpm the rest off hook up info would come with your new tach this is the same we use in servicing trucks so we have rpm while making engine adjustments rite next to us and to verify actual rpm against customers
i have found out after i contacted you yes cummins does makes a mechannic tach for that engine - you just need to get the right person at cummins!!