5.7l TPI in a 75 chevy truck.
My truck has a new wiring harness and 5.7l swapped in by previous owner

When I first bought the truck it had a two electrical issue:
1) heater circuit cause parasitic draw (unplugged the fuse "solved")
2) alt does NOT work when ACC fuse is plugged in (unplugged "solved")
..now the truck runs with no power drains
but theres no music and I want to get that working (only the music i dont care about anything else)


Is the only option to take out the manual of all the wiring and to go through ALL the wiring, to re wire?
Is it possible to completely just rewire the stereo directly to the batt or something easy like that?
Any advice or what the problem could be or where to start?


I lack time and patience to go through the entire harness plus i don't want to pull the old dash apart