I've had a couple of people express interest in this, so here's my write-up on the rebuild of the tail-light assemblies and conversion of the stock incandescent bulbs therein to LED clusters. Hope someone finds this useful.
History:
My '74 911 came with a myriad of neglect-related issues, including cracked rear taillight lenses. They were also U.S. spec, which I thought looked a bit odd given that the car has Euro-style front fenders. As such, at a bare minimum I wanted to replace the lenses with Euro-style ones. Here's what I started with:
You can see the cracks on the left-hand lens assembly here. Also the badly deteriorated and dry-rotted gasket between the lens and the housing - this is a common problem. You can also see that the screw hole for the center screw was "oversized" (for whatever reason by the P.O.), which required a large fugly washer in order to install a screw in that location.
The R/H lens - looks a little better but still weathered.
This is a typical housing removed from the car - there's a metal plate held onto the back secured by two screws. The wiring passes through this plate through a rubber boot. Since there is nothing that sits between the rear wheel wells and the back side of these housings of significance, they take a beating. The screws (holding the back covers on) tend to get corroded and the rubber boot is likely to be dry-rotted (proximity to the muffler/heat probably doesn't help here either over time). Once the screws are removed, you should be able to slide the back metal cover off over the wiring (carefully) and access the back of the housing. There are a number of spade connectors onto which the wires attach. These will be discussed below.
Inside the back of the housing - you can see the backs of the bulb sockets for (from left-to-right) the tail-light/brake light bulb, the reverse light bulb, the turn signal bulb and the running light bulb. There are small brown "circuit boards" at the back of these sockets, into which are cast the brass contacts for the bulbs, and the spade connectors onto which the wiring attaches. They are held in place with (brittle) bent metal tabs. In this photo, the circuit boards for the tail light/brake light bulb and the reverse light bulb have been pulled out already
Inside the R/H lens - you can see that some water infiltration over the years has done a number on the metal. You can also see the different bulb "compartments" that the housing is divided into. From left-to-right these are the tail/brake light bulb, the reverse light bulb, the turn signal bulb and the running light bulb (small one, normally sits behind a refraction lens).
You can see the condition of the metal here. Pretty bad. Oxidized and pitted. A bit of surface rusting. This will have to be addressed.
Another view of the exterior. These housings take a beating over the years since there's nothing in front of them between the housing and the wheel wells (just open space). Rocks & debris getting kicked up in there probably doesn't help matters.
Oooooh, this is gonna' be a problem. . . Turns out there was more to the "cracked lens" on the driver's side. So I sought out and got a used pair of housing off a guy on Evilbay. Not bad for $100, given that new replacement housing would run north of $800 for the pair. The replacement housings were in comparable shape to mine (minus the busted corner). Pitted/corroded metal, badly faded on the inside, in need of some freshening up. . .
