The book I'm looking at is from a set of four books (vol 1-4) and labeled as such:
1998 C/K Truck Service Manual, GMT/98-CK-4, Volume 4 of 4. Includes Engine and Transmission/Transaxle.
It's "two tone" blue in color. GM Authentic technical Service Information "seal" in the bottom LH corner. All vol's are 3 hole punched. Here's a pic:
Information page inside:
1998 C/K Truck Service Manual Volume 4. Published by North American Operations. General Motors Corporation. Warren, Michigan 48090. Copyright 1997 General Motors Corporation. Information cut off date 3/26/97.
Here's the ref for the adjustment:
Chapter 6, Engine Controls - 6.5
Page 6-2636, Para - TDC Offset Adjustment, sub para 13. (not trying to beat you over the head with a detailed ref, it's just an occupational hazard and such. An ex-Military tech should understand

)
Here's the passage as written in the manual verbatim:
13. Slightly (1mm equals 2 degrees) rotate the injection pump (use tool J 29872) and tighten injection pump flange nuts. Rotate pump toward drivers side; a positive (+) number, rotate toward passenger side (1 mm equals 2 degrees) in order to achieve a negative (-) number