Power from Taillight is wired to fuel sending unit... Check!

The way I see it

74 column on left, 65 harness on right

WHITE -------------STOP SWITCH----------WHITE

DARK GREEN---RIGHT REAR-------------BROWN

YELLOW/ BLACK-LEFT REAR--------------DARK GREEN

RED--------------------------------------TS FLASHER-RED

DARK BLUE--------------------------OUTPUT OF 4X flasher

LIGHT GREEN------------------------RIGHT FRONT--TAN

YELLOW---------------------------------LEFT FRONT---LIGHT GREEN

DARK GREEN------------------------HORN BUTTON--BLACK TRACER

I don't know if you 65? had? a 4x flasher. IF not, wire a fuse from a constant hot, through a flasher, and hook to that DARK BLUE. If you already have a hazard flasher, it should work OK if it is already wired, but you will not use the switch on the column.

You can check the colors to the switch with a continuity tester light

Make a truth chart to show what connects to what

With switch "in center" stop slight switch should hook to both rear lamps. Fronts should not hook to anything

With switch to left, flasher should hook to left front and left rear, and brake switch should still hook to right rear

Opposite for right turn

With column hazard turned on, blue should hook to all four lamps front and rear