87 454 Tbi. Problems, need your help?

[87crew4x4]

FSF First things first. Its a simple question, The engine tune up label says to disconnect the single tan w/ white stripe wire (to the spark advance I guess) something, something, inboard of the bulkhead. Can't find it, easily anyway. I need this to properly time the truck. And then I will try and find out why its running like it wants to rolled over a cliff. I have had quite a bit of trouble with it, I replaced the distributor and it ran good for awhile but I dont think I ever had it quite right. Now It is really acting up and I would like to start with the timing. Thank You.