Based on replies #63-66 makes me think it would be approximately 2 1/4"w x 3 1/4" L for the #3 hole. The important measurement would be width (of the tape roll) and the length would be wherever it was cut from the dispenser. Danny's reply #63 seems to be the best indicator so far. If it were me I would cut the 3" width down to 2 1/4" after cutting off about a 3" length.
I've been giving this topic a lot of thought in regards to what the roll width is. Given the line worker(s) had to pull a piece of tape off a dispenser and place over the holes, while in a moving environment, the last thing you want to do it trim tape. So, it should be set up where you only need to worry about one of two variables (being width and length) and that would be tape length. With that in mind I would think the tape width would be such that it would be easy to place up in the flat section at the shock hole to cover that area entirely (with the proper length of course) and yet it would also be wide enough to cover the #3 hole. And that shock area width is 2" (measured on my 67 coupe). So, the only thing the worker had to do is pull off a correct length and slap it on. Based on Danny's measurements, I would cut the width to 2 1/4".
Mike