If you have the cluster out don't give it another thought. LED's are the way to go. I got the set which works with the reostat but thinking about it now I should have just saved the dollars as I like them at the brightest setting. Using the old incandescent bulbs I could hardly see the numbers on the speedo and that was with new bulbs. With the LED's its like looking at the dash in a new car. Because the LED's are a cleaner white light the blue lenses in the cluster give the appearance of a nice blue light versus the bluish green of the incandescent bulb. These bulbs will last forever, burn cooler so no more melted blue lenses. They are also much crisper at the turn signal arrows.
Looks like you actually read the instructions ! Can I ask WERE THEY GOOD?
You can confirm these are actually hipoparts.com kits ! (there are others selling LED's - BUT THEY aren't the same)
Would like you guys to know you are dealing with a LONG TIME Mustang owner, collector and truely GREAT GUY in Bill ! It has been a tough time with the economy. I chose to actually use ALL LED'S in my 1969 - as a favor to Bill. Car looks great ! (and I'm not taking them out)
Mark
P.S. Though there isn't a vendor area Bill has a great chart for our cars that could be posted (IF OK) it really helps for those that just want to replace certain bulbs (as you go) during component repair