I had reversed the brake light pigtail in my 68 and it caused the parking light circuit to light up also. I switched it back and all was well. That may or may not be what happened to you. I had the brake issue as well. Are the brakes working very well? You may be losing fluid through a leaky cylinder.
Same thing happen on me on my 72 when I got it, just reversed the brake light pigtail & took a look at my grounds for the park lights & it fix it right up!... Look also if you got the right # bubs in park & brake lights!
