A couple more of the potentiometer/rheostat.

Interesting. There is a difference there from the one I have. So there should be 3 wires? Curious if we are using the same unit. All my research show the dial as a two wire and the power is applied to the box itself thru the 3 wire bundle on the box.

The three from the dial go into the box and then three out positive,negative and coil.
Your correct the early points style has two wires on the dial. All mine are 644's the early electronic ones.

There is definitely a difference. The 28770 has a two wire dial, with the box having a two wire lead, red and black, and a three wire lead red, black, and green. The install instructions posted by Kurt may be a bit different then how yours installed I'm guessing. Question still is, can I use this with a Dave's Small Body HEI. I'm going to contacted Dave anyway to be sure at least about that. I don't want to ruin anything. Thank you for your insight. This may help others down the road.

Just a short note to say I finally found a decent example of the #644. Happy as a clam now. Dated 8/98. Curious if they were made later than that. I was just reading a little history about Mallory and it's a bit confusing on what banner Mallory was under when this was made.