charging system woes

[RBrandon]

my '93 302 ho is having issues. Past couple of days going to work it the discharge light started coming on and off. First day on for a minute or two and off for a while, then on again. Next day it would come on for longer periods. Today on the way home from work it came on and stayed on for 45 minutes. I have a brand new duralast and I drove home with nothing on but was still surprised I made it home. I couldn't find my multimeter to verify, but I figured the a the diode was getting hot so I replaced the alternator (V-regulator attached to back) this evening. No change. I finally found my meter and even though the discharge light is on and the voltmeter reads around 10 V, the meter read 13.5 (fluctuating some to 12.5-ish) at the battery terminals when my wife held the tach around 2k. At idle it wasn't much over 12V. So I know there isn't a whole lot to the charging system but I can't for the life of me find my Haynes diagrams. I am thinking high resistance open somewhere but haven't found any hot spots in the wire. Then theres the chance of a bad ground, but without the diagrams I really don't know where to start. Any pointers in the right direction or things I can rule out would be greatly appreciated. I have a degree in electronics and used to work on aircraft but have lost too many brain cells working for the phone company and am too damn tired this week to start blind on my only day off before the start of what is going to be another long work week. I haven't even had time to put the rack and pinion assy sitting in my living room on my stang and that should probably be done before I kiss a tree. Any help would be appreciated.