1987 F-250 Speedometer Issues

I recently bought an 87 F250 for a utility vehicle, and although it seems to be in decent mechanical condition, it has a host of electrical and interior issues. The two I am most concerned about are the speedometer not functioning and an issue with the brake/turn signal lighting.

The truck is a regular cab, 460 with the 4 speed manual tranny and 4wd.

Speedometer:

I have checked the cable at both ends, and the issue is not at the speedometer head, as I can make it function with my hand. The cable is intact, and is interfacing with the drive gear at the t-case. The gear looks fine, and the green worm gear inside the t-case appears to be in fine shape (not that I am an expert in these things though). What else could be the problem? My best guess is that the problem is in the t-case itself, and is more work than the truck is worth, and that is why nobody has fixed it yet.

Brake/Turn signal lighting:

I know that anything electrical is a can of worms, but I will try to explain the issue. When I bought the truck, the turn signals and the hazards were not functioning, but the brake lights worked fine. Of note, however, was that the front turn indicator lights would both light up upon depression of the brake pedal, and the interior dashboard indicator lights would also illuminate. I started poking around under the dash to discover a rats nest of 3rd world automotive electrical work. One of the wires leading from the brake pedal arm switch had been cut, and wired into a replacement cigarette lighter plug, as the ash-tray is missing. I reattached this in hopes that it would remedy the problem, but I still have no turn signals and now have no brake lights. I have printouts of the turn signal wiring diagrams, but I don't know where to begin.

Any advice on where to start, or methods of tracking the issue down would be much appreciated. I am tempted to just take it to a mechanic, but I bought the truck for $1600 and don't want to sink a bunch of money into it.

Thanks!