Mopar Noob - 1970 Dart Swinger

:welcome: to the fray - everything you mention is 100% doable. Personally, I would search out (Google) an aftermarket wiring harness.. messing with a 50 year old harness can be sketchy... gut it and install all new. The interior - Google it of course, but Legendary Interiors comes to mind. The brakes - yes, there are two different bolt patterns - so you want to stay small bolt pattern and have disc brakes.. others will chime in here - I am fairly sure that that is also doable... again, some time spent with Google is a good idea. And/or - start a new thread on here asking for help with that specific thing... TONS of good people with 10 tons of know how!