If I was doing the wiring, provided the following conditions are true.

1. There is no need to make the wiring easily reversible.
2. There is no need for the wiring on the old ignition circuit.
3. You are just needing the main 12VDC switched source for the Haltech.

Here is my thinking.

1. Buy two latching 1 pin connectors from Vintage Connections. 
2. Buy some extra male and female pins for this type connector. 
3. Buy an open barrel crimping tool if you don't already have one. (Amazon link for a crimping tool)
4. Buy an inline fuse holder.
5. Identify which BW wire at the engine harness/dash harness is the one on the ignition circuit, noting the connector and position. (I'll detail how to identify the wire later.)
6. Back out the pin for that BW wire from the connector on the engine harness side. (Vintage Connections tool)
7. Cut a short length of wire, maybe 3 to 4 inches. On one end, crimp a female pin onto the wire and insert into the female 1 pin connector. On the other end of the wire, crimp a pin that matches the type you backed out in step 5, and put it into the engine harness connector to replace the wire you backed out.
8. Strip, crimp the pins, and put the male and female connectors onto the wires of the inline fuse holder.
9. On pink Haltech wire, crimp on a pin and attach the remaining connector to plug into the one on the end of the inline fuse holder.
10. Use no larger than a 10A fuse in the inline fuse holder.

26 minutes ago, Blitzed said:

Duffy,

Have a 73, so don't want to assume your stock ignition harness is the same wire color combo. Remove ignition switch cover behind the steering wheel and test the 5 pin connector plugged to the back of the ign key switch. Believe it's the B/W wire for 12v switched on (it's been a year and reassembled). Attach the pink wire from the Haltech ECU. 

It is the BW wire. However, if Duffy connects the pink wire at that point, there is no protection for the wiring. That's why my instructions are as detailed as they are. Mind you, I do controls engineering for emergency power, so I do look at how to prevent the magic smoke from escaping from the wires.

 

Agree without the Haltech premium wiring harness (safeguard investment). The prem harness runs all ECU connections back through intergraded expandable fuse and relay box (pink ign wire 12v switched and all battery connections included). 

Not not sure what Duffy has for a harness?

 

Yeah, I have already de pinned the B/W wire from behind the ignition switch, I believe I have a few extra connectors for the stock pins.  So install it there, inline, but fuse protect it.  That makes perfect sense to me.  

28 minutes ago, Blitzed said:

 

Agree without the Haltech premium wiring harness (safeguard investment). The prem harness runs all ECU connections back through intergraded expandable fuse and relay box (pink ign wire 12v switched and all battery connections included). 

Not not sure what Duffy has for a harness?

 

It has an expandable fuse and relay box.  I have 4 open fuse spots.  2 open relay spots.  

Just now, duffymahoney said:

Yeah, I have already de pinned the B/W wire from behind the ignition switch, I believe I have a few extra connectors for the stock pins.  So install it there, inline, but fuse protect it.  That makes perfect sense to me.  

By removing the BW wire from the ignition switch, you also remove power from the following:

1. Tachometer positive
2. Turn signals
3. Voltage regulator (If you did the internally regulated alternator swap, this is used as the switched source for the alternator.)

You'll either need to use a Haltech switched source and find a place to connect into the wiring (Please don't hack the wiring.) or take a path like my directions.

My basic plan for the pink wire. 
 

Using the B/W spot for my pink wire. Then use the haltech fuses to give 12v to my iac. 

10 minutes ago, duffymahoney said:

My basic plan for the pink wire. 
 

Using the B/W spot for my pink wire. Then use the haltech fuses to give 12v to my iac. 

And you will not have

1. Tachometer positive (tachometer function)
2. Turn signals
3. Proper alternator function.

Hi Duffy,

Do not remove the B/W wire from the connector, splice into the wire using a copper U shaped crimp connector and heat shrink. Leave the connector intact for all other functions. This connection (pink wire) will only power up the ECU when the key is in the on position. Again, I'm safe guarded with the fuse box inline on the harness. Running for a year with this config, no issues, blown fuses and all stock electrical components function. 

Don't touch your tach, give me a call. 

2 hours ago, SteveJ said:

And you will not have

1. Tachometer positive (tachometer function)
2. Turn signals
3. Proper alternator function.

Well I want alternator and turn signals! Tach is wired for my coil on plug.  It works perfectly.  

 

I think my next step is to ohm check all the other ignition wiring that toned out and post the data.  

19 minutes ago, duffymahoney said:

Well I want alternator and turn signals! Tach is wired for my coil on plug.  It works perfectly.  

 

I think my next step is to ohm check all the other ignition wiring that toned out and post the data.  

You said before you are driving the tach from the coil on plug. That is the signal, but the tach needs 12VDC to power the discrete components to read the signal, unless you have another wire from the Haltech providing 12VDC switched to the tach.

I suggest you consider my solution detailed earlier rather than splice into the harness. It's more work the way I suggested, but there is sound reason behind it. 

Steve, is this your idea? I try to not cut any stock wires or drill any holes. I did my entire ITB install without a single new hole in my low mileage series 1.