Kids and their computers.
Amps do the work not volts. Points are designed for 4 amps whether it's a 6v system or a 12v system. There is only a minute difference in microfarads in the early Delco distributor condensers no matter which voltage. I converted my M to 12v several decades ago and still run the 6v part numbers.
The problem comes in with switching distributer brands. It shouldn't matter but somehow different manufacturers used different values and even though they fit they don't work well together.
Echelon RR 174 is the correct part number.