What is this harness called

Mustang 1968 Firewall Headlight Wire Loom to Headlamp w/ Tach w/out GT C8ZZ14290C 189.95 Each
Mustang 1968 Firewall Headlight Wire Loom to Headlamp w/out Tach w/ GT C8ZZ14290B 184.95 Each
Mustang 1968 Firewall Headlight Wire Loom to Headlamp w/o Tach w/o GT C8ZZ14290A 164.95 Each
Mustang 1968 Firewall Headlight Wire Loom to Headlamp w/ Tach w/out GT C8ZZ14290D 209.95 Each

Any of those will fit the bill.....your choice depending upon the options you have/choose to add.

If you get the tachometer wiring harness that also has the wiring for the fog lights then you will just have all the wiring for those options if added later but you don't have to use them at them moment. Worst case scenario is that you might have to jumper the tach leads to get the car to run....I'm not sure but most of Ford's tachs of the period were serial hookup and were inline in the ignition wire, if this is the case then either jumpering the tach lead will be necessary unless there is a way not to hook that part of the harness up. Someone with more knowledge of 68 cars needs to chime in on this one but I know there is a way to use the harness without using the tach.

The main difference in the tach/non tach harness probably has more to do with the idiot lights for the "ALT" and "OIL" instead of the tach.

I just put a factory tach in my '67 and you have to do some rewiring of the non-tach harnes IF you want to use the idiot lights. If you wanna use an aftermarket ammeter, leave the existing harness alone.

Keep in mind though that if you change this harness, you also have to change the under-dash harness and that's more like $400-$500. I just rewired what I needed to using the factory wiring schematic for the idiot lights.

You also need a different oil pressure sending unit, but the wiring should be the same.

The tach itself does exactly what the previous poster said...it wires into the ignition switch and does not connect to the underhood harness at all.

First check the dash wirng loom for a tach and gauge hook up.
There were some that got the full harness when the line ran short.

If there is no loose extra connections then it's a plain one.

The wire in the harness needs something to connect to.
They had many differant packages back then,
And if it had gauges,tach, sportlamps, ect.
The wiring was provided and used, Manufacture's have found it easier and less costly to have one basic harness that you could add on your extras too.

And yes if you use the tach harness you will have to hook the end to a tach or do a feedback loop to make it run.

PB

you may need the underdash harness because A) the current one may not have enough connections for some accessories as stated previously
B)to "plug and play" so to speak, the engine compartment harness not only has to have the mating plug on the under dash (and the under dash to the instrument panel harness), but it has to have the RIGHT mating plug. For example, when I rewired mine, I had to yank some of the pins out of the white plug on the instrument panel and rearrange them to make the idoit lights work. If you switch the engine compartment harness, you'll have to do that for everything in between if you don't change the other harnesses.
In my opinion, unless the car is going to lose points in a show because of incorrect wiring, wire the fog lights independantly unless you are lucky enough to have the "bigger" harness. Wire the tach, and rewire the idiot lights if you want to use them (or use aftermarket guages for oil pressure and amps with fewer mods). I have an article somwhere that I'll try to locate; it describes in pretty good detail about how the rewire is done, you need some resistors and stuff, and switch some wires around between the alternator and voltage regulator. And again, a different type of oil pressure sending unit.