Weird electrical gremlin

[wowitsaboy]

okay so I converted my non-running auto s13 to 5speed and running motor installed. I got all the harnesses in and ran into my first problem: starter had no power, I rigged a starter button with direct power from the batt. second problem: the cluster doesn't work, no reading or lights, no interior lights, tail lights, and headlight motors don't work. if I rev the motor to about 3k (judging by the sound) all these problems go away and everything works/ comes on, but is if I press the brakes everything stops working again.

I'm fairly certain there is a short some short or grounding issue. but where is my question.

my hope is that someone has run into this before and point me in the right direction, but any insight or help would be great. thanks