Good looking truck! I love the first generations!!!
This is from BradMPH's thread called "Rebuild, replace, refresh" or something like that of his prized "Mitsy"
Here's the link to his whole build.
http://www.mightyram50.net/vbulletin...ighlight=mitsy

Page 4, post #87 describes the ported vacuum advance.ported_advance.jpg