OK here is my 2 cents. I am trying to be helpful, but not sure how tough the moderator is.. but I think someone already put a link to my site so I should be OK. Forgive me but some websites have taken my help as Spam and banished or even removed my posts.
Others have appreciated my tech help. I never know which it is and if I step over that boundary, I apologize and ask the moderator to remove the offending link but not this tech help.
First off I have rewired a number of Fords.. and for some reason a lot of 68 Mustangs.. more so than any other year and not sure why.
That said, After rewiring numerous cars I wrote this tech tip ( But to answer the question I should mention there is a full FAQ for whats different about the harnesses, how to wire up the turn signals, and where you can download my universal wiring booklet, etc.. at:
EZ2Wire Your Universal Hot Rod Wiring Harness Specialist - Painless Savings and Painless Installation
On that aspect. Wiring diagrams for most modern 65 and Up FoMoCo products can be found at :
AutoZone.com | Vehicle Selection - Year
Select your vehicle and go to the side navigation for the manuals/diagrams
Also this website has a great list of pre-65 Ford and Edsel wiring diagrams.
wiring diagram index - The Old Car Manual Project
The directions for the Painless Diagrams are :
65-66 Mustang : http://www.painlessperformance.com/M...0526Manual.pdf
67-68 Mustang : http://www.painlessperformance.com/M...0556Manual.pdf
69-70 Mustang : http://www.painlessperformance.com/M...0557Manual.pdf
That all said.. the differences in Wiring harnesses can best be said in my wiring FAQ on my website but the short and sweet of it is this.
The Painless Mustang harnesses use a standard (actually thier cheaper basic 14 circuit) Universal wiring harness trimmed to fit with a few Mustang Plugs, American Autowire now sells a really nice 67-68 Mustang harness and its based on their Power Plus 20 harness. The Painless and American Autowire run about $600-$750. Personally I think the American Autowire is better thought out and a nicer overall harness.
That said you can just as easily rewire using a basic Universal
harness. Because be it the EZ Wiring (not to be confused with myself EZ2Wire), Kwik Wire, Painless, Hot Rod Wiring, Its-a-Snap, etc.. all are different styles of Universal harnesses.
ALL use GM Color Codes.. that includes the "Mustang harnesses from Painless and American Autowire".. this is because GM standardized thier colors across the board in the mid-60s while Ford color codes varied wildly, same holds true for plugs and connectors.
Most are labeled every so often down the wire (Hot Rod Wiring is one that doesn't label.. ) Where the difference is in the harnesses is truly the wire. The cheaper the harness the cheaper and thinner the wire.
The fuse panels are also a big seperator between the harnesses. EZ-Wiring (Which I do NOT sell.. ), Its-a-snap, and some Painless harnesses use MINI-ATC fuses and not full size fuses.. thier fuse panels tend to be smaller but also less robust due to the thinner plastic and smaller fuses.
Kwik Wire, the Painless Muscle Car harness, and all American Autowire Power Plus and Highway Series harnesses use full size ATO fuses and thus have slightly larger fuse panels.
My favorite is the KW14STD, 14 circuits, wire is much thicker than most harnesses (especially the painless and EZ wiring harnesses), and its hand made in Wisconsin by Kwik Wire. Unlike most harnesses which are made in China.
What I have done that is different, is that I list a KW14FORD. The KW14FORD is a KW14STD harness, but I have used my experience in rewiring Fords, to know what connectors I need to reuse their factory plugs. So instead of selling a customer a harness with GM plugs and connectors they cant use. I sell them a harness they can use with a ample selection of connectors (In some cases Ford specific like the
large round female connector on the 67-68 ingition switches) and Ford plugs (like a new Ford Voltage Regulator Plug) so use of the KW14FORD is easier for the Ford owner to install.
Now should mention one thing.. No matter the harness.. the likely hood its using a GM Color Code is about 85% (the other 15% of harnesses would be all Black or have thier own odd ball color code, usually red, black and yellow). The point being is the Painless Mustang harnesses use a GM color code, so you can simply use their directions for any Universal wiring harness because for the most part the color codes will match and if they don't it doesn't really matter since they are also all labeled by circuit.
Hope that helps and if anyone has any questions feel free to email me and ask.