Anssi, that Hemieddy fellow on e-bay always has the headlamp harnesses listed on e-bay (MW specific since they're longer). I would try and find a nice original rear harness. Maybe "borrow" one from your '63 "parts" cars?

'70 Super Bee 440 6 pack 4-spd 4.10 Dana N96 EB5
‘70 Super Bee 440 6 pack 4-spd 3.54 Dana FC7
‘70 ‘Cuda 440+6bbl 4-spd 3.54 Dana N96 EB5 V1W