Well I spent some time on this, I hope it helps.
I put both survivor '68 cars on a lift. I was pocking my head up on the left side frame rail of Raquel and discovered a piece of the tape just laying there on top of the frame right next to it's original install position.
I delicately pulled it down. I measured it and it seems to me to be 3-1/8th" Left to Right X the foot print of the tape on the under body at 2-1/8th" Front to Back. Could it have shrunk some in 50 years? If it did, then I say 3-1/4" X 2-1/4". The picture shows the tape. So it's clearly not 1.5 or 2 X 2 That's the best I have on both cars. Danny