The following directions should provide the necessary information to modify your 72 harness for use on your 70.
If you look closely at the wire side of the dash harness bulkhead connector (separate the fuse block from the bulkhead connector) You should see letters marking the rows and columns. The rows are A,B,C and D. The columns are S,T,U and V for the forward lamp harness and W,X,Y and Z for the engine harness. The following instructions will refer to these coordinates.
Includes wire color, engine side connection and dash side connection
You also need to move wires in the cluster connector to change from lights to gauges.
FORWARD LAMP HARNESS BULK HEAD CONNECTOR
AS – No wire (Should be black wire for key warning buzzer. Your warning buzzer will be under dash,)
BS – Dark Green – temp sensor or temp switch / temp gauge or temp light – Move from CZ
CS –No change (Light Blue –LH dir signal)
DS –Black – J-block /amp gauge –Move from DX Forward lamp harness wire to be added. Gauge cluster harness only
AT –No change (Black grounds at horn button for horn relay)
BT –No wire
CT –No change (Dark Blue –RH dir signal)
DT –Black/dark Blue/White (looks like Black/White) –horn relay / amp gauge –Move from CX. Forward lamp harness wire to be added. Gauge cluster harness only.
AU –No change (Light Green -head light high beams)
BU –No change (Brown –running/marker lights)
CU –Brown/White –voltage regulator / ignition switch (The brown white wire from the ignition switch is a resistor wire, supplies power to the voltage regulator when key is on) -brown wire to GEN light (light harness only) –Move from BT.
DU –Tan –brake dist block / brake warning light –Move from BS
AV –No change (Tan –head light low beams)
DV –Red –Main power feed to dash –Move from WD
ENGINE HARNESS BULKHEAD CONNECTOR
AW –Purple –starter solenoid S terminal / Neutral safety switch –Move from AZ
DW –No wire
AX –No wire (would be TCS)
BX –No change (Pink to ignition switch / engine side has white/orange /purple to coil)
CX –No wire
DX –No wire
AY –No Change (brown –coil / tach) Engine side wire to be added. Gauge cluster only.
BY –No Change (dark blue oil pressure switch / oil warning light)
CY –Yellow –power to wiper motor / wiper fuse –Move from DS
DY –Light Blue –wiper motor (washer pump) / wiper switch –Move from DT
AZ –No wire
BZ –No change (orange blower motor / blower switch) Used on heat only cars, not used on A/C cars.
CZ –Dark Blue –wiper motor / wiper switch –Move from CU
DZ –Black –wiper motor / wiper switch –Move from DU
Note: The wire in AY is found in a gauge dash harness only it is for the tach to coil. For a 70/71 harness this wire is not routed through the bulkhead connector. It is routed through a hole in the firewall.
Wires in DS and DT are for the AMP gauge, also gauge harness only wires. You will need to add these wires from the cluster connector to the connections under the hood.