68 camaro harness help!

[P.J.]

I installed new harnesses on my 68 Camaro front enjine,under dash ,and rear harnes/ I followed the GM assembly manual. When I put the power on the marker lights
in the front fender are on. The 20 amp fuse (top Left) CLK,LTR BLOWS.Also when I put the battery cable on the positive post the horn honks once.The interior light wont come on. I have checked the grounds, the streering colomb wires, the interior light wires and the lighter wire.I even removed the horn contact. Still the same thing happens everrything else works great.could it be a factory wire mix up?? I purchased them from Factory Fit.
Any sugestions
Peter