Distributor help nededed

I tore my distributor apart to change the pickup coil. On the base there is the gear, and an inch or so there is a ring that gets a roll pin (looks like a donut with a ridge on it.)
Putting it back together, I am not sure if that ridge does to the bottom of the distribitor housing, or the narrow end goes up. Does anyone have a dist. handy to look at? This is for a 1979 400 engine. Goes in a F150 pickup truck. (In other words, that round device is wider on one side than the other. Does the wide side, or the narrow side face toward the bottom of the main distributor housing?)
Thanks
Mark
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that
engine.
The narrow portion is closest to the drive gear, the flanged end is closest to the housing.... .
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Does
is
narrow
Like this.....
http://home.tir.com/~artemus/Impeller/DSCN2355.JPG
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Thanks to both of you. Now I can finish puting it back together. I thought it went like this, but just was not sure. I should take a picture myself before I rip things apart.
Mark
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