That HEI in the tech tip shouldn't be a first choice. The extention is slightly undersize(.007") and doesn't support the gear as well as a solid shaft. This example happens to be in an external-coil unit.
[img]http://home.earthlink.net/~roadruner/Dist2.JPG[/img]
The one on the left has a much smaller, lower shaft and shouldn't be used either. The .012" step down on this one is hidden when the gear is in place.
[img]http://home.earthlink.net/~roadruner/Dist1.JPG[/img]
The only one that should be considered, is one with a .489-.490" shaft, the entire length, such as the stock point dist on the right, above.
[img]http://home.earthlink.net/~roadruner/Dist5.JPG[/img]
The internal-coil and the external-coil housings have a different key slot for the cap. The external-coil housing has the slot, next to the vacuum advance. The slot on the internal-coil, as seen on the lower one, is much farther away. I'm using a internal housing, with external-coil and cap, with no problems.
