@65AFX, the way in which I make my first and sample style of trunk weatherstripping for the necessary cutouts is in the following manner.
1. Position the new seal approximately 3 inches to the right of the trunk lock mechanism.
2. Working in a clockwise direction, lay the new seal on top of the old seal if it is still in place. If not, then it is actually easier, position the seal pretty much where it will be glued to the rain gutter.
3. I use wooden clothes pins, approximately every 6 inches, I position a pin to hold the seal in place.
4. Be very careful not to stretch the seal, especially in the corners. If it gets stretched too tight, it will want to lift in the corners producing leaks and making more difficult to glue to the body.
5. Proceed around the perimeter of the trunk lid in that fashion.
6. Once completely around the perimeter, cut the seal so that you will have approximately 2 inches of overlap.
7. Take a silver Sharpie or other marking device and mark the areas of the seal in which the lip needs to be remove. There may be various areas depending upon the year model and body style your working with.
8. Once the seal is marked, remove the clothes pin and your ready to start cutting the seal. With a new razor blade, cut a perpendicular into the lip so that your to the flat area of the seal. Then score the lip with the razor blade so that the flat area of the seal is your reference point. Continue in this fashion, until the lip is completely removed. Then move to any other areas that needs to be removed and proceed in a similar fashion.
9. Once the necessary areas are removed of the lip, you can test fit your seal again to make sure that it will fit tightly to the rain gutter and trim as necessary.
10. If everything looks and fits good, then you can glue the seal in place. Make sure not to stretch the seal in any one area.
Personally, I had rather cut and make the seal one continuous length vs vulcanizing the pieces together. The original seals were done in that method using a different technology using a rope to remove the seal from the mold. We have worked with vulcanizing the ends together, but the process does not always yield a cosmetically appealing piece that will possibly come loose eventually.
In regards to the seals, the 62 B-Body is a one year only piece which is unique to itself. The style in which you will be working with was used from 1963 to 1969 and some of the 70 applications.
Hopes that this helps and one other thing, if you can recruit a second set of hands to hold the seal in place as you work with it, it will yield a better fitting piece and make the job much quicker. Good luck.