This was a problem I am having w/my Belvedere. I bought the painless dash mount 4 toggle system but was not happy w/how they had the start button wired(hot all the time). I changed that and the fuel pump circuit so that I have to flip one switch before either are hot.
Then I find out my factory harness(headlights and taillights)was jacked and now I need to get a 4 circuit set up(headlights, taillights, breaks and turn signals). Yeah try locating that. On Tuesday I will call Auto Wiring Solutions(they have a 4 circuit) and see if this will work.