Underhood Wiring Harness Wrapping Tape Q.......

[Mr70]

They originally never used adhesive tape.Sounds like yours is still authentic.It's only a few mils thick and designed to stretch and absorb over itself.
DON'T use PVC tape,as it is too thick and unreliable.It also stands out like a sore thumb to the trained eye.
You can buy harness wrapping tape from many suppliers today,but chances are they all got it from Lectric Limited here in Bedford Park,Il.
Click on the rotating "Click Here" and scroll down to "Repair Components",then down to "Harness Tape",Part #R58276S.It originally came in 3 width sizes and you can still obtain anyone of them today for roughly $12.00.
1" is the most commonly used on GM vehicles.