Strange starting issue

Doesnt it all go through the amp gauge?

check continuity on'em but....maybe pull the feed from there and go through the painless box 1st?

I have a '67 myself...and after all the dim headlights and shorted charging system wiring...I finally just had the whole car rewired 'heavier gauge' and had a headlight amplifier installed. Now I can run my 800 watt stereo, msd, heater, and whatever else I want with no voltage dip or dim gauges....cost $575 but came with a lifetime warranty, which is almost unheard of in electrical work.