Been a while since I posted on this thread, but I keep checking back to see what's new.
I did my 78 a year ago, in 2 tone green, with the dark green base first and then the lighter green.
I taped off the panels and simply repeated the process a second time with the lighter color. Removed the tape using a cloth wetted with mineral spirits to soften the adhesive and prevent pulls on the new paint.
Once the tape was off, I wiped the panels thoroughly with MS to remove all adhesive and did the final wet sand and polish on the entire panel.
Other than removing the tape carefully, it wasn't a big deal. Just a repeat of the original process on a smaller area.
The separation line on mine is covered by the trim, but it came out clean and straight. Make sure the tape is pressed down at the edge and there shouldn't be any bleedover at the edge.
To do the stripe as your pic shows,I would wetsand
the line smooth at the separation and then tape half the strip width on either side of the line.
This will cut down on the appearance of a step at the stripe.
My , there are a few others that have done hood stripes and body stripes that have a few pointers as well.
Stay safe and good luck with the painting.