If you are mechanically inclined, you really don't need a manual for
the injection pump on that year. I have R&R the inj pump on my 89 and
it was no big deal. The important thing is to turn the engine over by
hand(you can get the turning tool from Cummins or TDR) amd then lock
it in place with the index plug down on the left side just below the
pump. After that, it is pretty simple, mark all your lines, take some
pictures for back up. Disconnect everything and slip it out. Mark the
position of the pump drive gear for timing. The biggest thing here is
it is time consuming, but not rocket science. Don't forget to pull the
plug back after reinstalling the pump, don't forget to pull the plug
back , don't forget to pull the plug back.
Also, if necessary, you can probably find this infor on TDR or
dodgeram.org.    JMTCW
DON'T FORGET TO PULL THE PLUG BACK !!!!!