Dashlights & Headlights!

["lynx@domain.elided" <lynx@domain.elided>]

  Hey Guys,
   Hopefully someone can help me out. I've got a '69 IH 1200series 4x4 truck.
recently the dash lights started to flicker slightly at idle. The headlights did a little too. The amp gauge would bounce around crazy from side to side. However when driving down the road everything seemed fine. This has went on for a couple weeks right after a changed the alternator. ( never noticed it before then anyway). I also had to buy a new belt because the pulley on the new alternator is a different size. Would the size of the pulley mess things up that bad??? (The new pulley is a little smaller in diameter.) So early this morning I'm going into town and when I come to a stop the headlights don't just flicker they go dim. A couple seconds later the got bright again. So today I've cleaned my ground, put a ground strap on from the engine to the frame, and replaced the voltage regulator... and I think it might be worse than it was !!!
 Am I on the right track??? What else should I try???  Thanks guys!
   Andrew Thomas (lynx@domain.elided)
   69 IH 1200 pickup
   345/ 4Bbl/cam/etc
   4:09 gears & Granny gear 4-speed
   "My Lttle Stump Puller"