Looking great!
From the description of your problem, i would start with the easiest things, making sure the dash has a ground, anf the indicator lights aren't burnt out.
After that i would suggest that you gave two options, either to try to correct the original wiring or just being bad some power for the dash but indicators.
If all you want is the missing indicators I would check if you have power at the switch or on the steering wheel and steal from there for a high beam indicator. I dont remember if the flasher is before or after the switch on the column, but either you can get power from there to the dash or just take it from somewhere further down the harness where the light blinks. 3 wires plus a ground, shouldn't be so difficult