That plug is the number I used in my drag car (G.M. aluminum heads), it is a reasonably "cold" plug, worked well with the 13:1 C.R.
Here's a "cut & paste" from O'Reilly Auto parts:
https://www.oreillyauto.com/
Copper Plus
Champion Copper Plus Spark Plug
(Quote)Part #120 (N5C)
Line:CHP
Check Vehicle Fit
Details
Product Information
Warranty: 1 Year Limited Warranty
Unit of Measure: Each
UPC: # 37551000869
Material Grade: Copper
Hex Size (in): 13/16 Inch
Hex Size (mm): 20mm
Thread Size: 14mm
Center Electrode Design: Standard
Thread Reach (in): 0.75 Inch
Thread Reach (mm): 19mm (.749")
Number Of Ground Electrodes: 1
Preset Gap (in): 0.023 To 0.028 Inch
Preset Gap (mm): 0.58mm To 0.71mm
Short Style Spark Plug: No
Resistor Plug: No
Ground Electrode Tip Material: Nickel-Copper Alloy
Heat Range: 5
Center Electrode Core Material: Nickel-Copper Alloy
Seat: Gasket
Ribbed Core Nose: No (End quote)
(Add) Eric was correct, after all F-M makes these Champion plugs!
Thanks, Gary in N.Y.
P.S. I believe the "13/16" being mentioned above is most like the wrench size, just a hunch here though??