What to do under the dash besides this?

I would also contemplate replacing the harness if you have it that far down. The crimp fittings were never made to last 50 years, many of them are likely high resistance now. The dangerous ones are the ones that are high current (ammeter, AC clutch, blower fan) and get high resistance. You can get the AC and Main harness for for the '73 from Year One or Classic Industries (both M&H harnesses). The main harness is NOT cheap but I always bite the bullet and replace them.