Help with light issue

[Sooner66]

Hello everyone! I'm new, well kinda. I use to use the name hotrod73. I haven't been on here in years. I'm from norman Oklahoma and just got a 66 c10. Hoping I can get some help from you guys!

Just picked up a 1966 c10 from a buddy. Hoping someone can guide me in the right direction for some help. The brake light assembly is the 40 led conversion ones, don't think this is the problem but the brake lights work when you hit the brakes but do not stay lit up with the lights on. Only when you hit the brakes. Also, the dash lights and cab light do not work either. Could these be related? It has a new painless wiring kit installed in the truck so maybe the previous owner wired it wrong or something else? Where would be a good starting point on this? Thanks guys!