Here is a TSB on the plug gap
Date: SEPT. 1992
Corporate Bulletin No.: 266401R
ASE No: A1, A8
The following represents revised information for SECTION 6D4 in the 1991 S/T service manuals.
This information replaces the plug gap information found under "Spark Plugs" in "Specifications."
The gap for plugs used in the 4.3L (LB4) (VIN Z) engine should be 0.035 inch, not 0.045 as stated in the manual. Torque remains as stated.
I would recommend using A/C delco brand spark plugs.