So in diagnosing the many, many issues this vehicle has, I noticed that the side markers and brake lights will stay on when the doors are opened, when I remove the fuse for the interior lights they turn off, but will work when they are supposed to when I use the headlight switch. Any ideas?

 

Is there any interior lighting that is not stock? Sounds like someone tried rigging some interior lighting to come on when the doors are opened AND come on when the lights are turned on, and if you don't do it correctly with relays, then you get this issue (I know, when I first did mine I did it wrong, and all the park lights come on when the door is opened.

What happens, is that the door switches for the interior lights are switching a ground, while the headlight switch is switching a positive. You have to use a relay to change the door switch activation to switch a positive same as the headlight switch. BUT THEN you also have to wire in a second relay to activate the interior lights, otherwise the opening of the doors will backfeed power from the first relay through the headlight switch and make all the park lights come on.

So - dig in under your dash, and look for rigged wiring attached to interior add-on lights or whatever, also look at the headlight switch wires and see if someone has connected anything in with those wires.

Here's wiring diags for almost everything that might help: http://www.austinthirdgen.org/index.php?pid=19