Here are a few photos of the original drain tubes. They are molded rubber which of course likely have dried out and crumbled over the past four decades. The tubes insert in four oval holes in the trough below the side glass. Two tubes attach just above the wheel well and the tubes drain forward over the wheel well and then drain into the interior of the front half of the quarter panel. Two other tubes drain from holes just below the c-pillar and drain rearward and dump through holes in the floors just below the taillights. Note: the end is broken off on top tube, when whole it would look like the one below it.
Here is a close up of end of one of the tubes where it snapped into the oval hole in the trough.
The holes in the troughs look like this.
That oval shape then is the main challenge in rebuilding the drains. If the holes were simply round, any number of plumbing fittings could be had to quickly and easily fill the holes. There are probably many methods that could be used to rebuild the drains, but outlined below is my method. I spent less than $25 on materials and used materials easily found at any decent hardware store. I designed my system on simplicity and longevity. The materials consist of nylon plumbing fittings, two 90-degree and two straight fittings, all with a 3/8" threaded end and a 1/2" barbed end, enough clear vinyl tubing to make four drain tubes and four wiring conduit nuts of the appropriate size to fit the threaded end of the nylon fittings.
The first step was to cut two slots vertically down through the threaded ends of the nylon fittings and then make one horizontal cut to remove one quarter of the threaded section. This allows enough threaded material to remain to be able to thread the fittings into the nuts yet creates a window through which the water can drain without having to rise to the level of the top of the fitting to run down it. The troughs are fairly deep and the drains holes are slightly recessed, but these relief cuts allow the water to drain easier and more completely.
Leave enough threads below the relief cut for the nuts to make full thread contact when fully screwed down.
The next challenge is to install the drains. I used two straight fittings at the rear and two 90-degree fittings at the front drains. I pointed the angled ones forward so the hose could drain forward like the originals. Getting at the holes and threading the fittings into the nuts can be a bit of work. I ended up grinding the edges down on all of the nuts so they could fit down into the floors of the troughs more completely. The troughs will hold the nuts in place so you can thread and turn and tighten the fittings up into the nuts. Here is how they look installed.
Of course you will notice that the drain is hardly water tight to the oval holes. To seal things up, I spread body seal caulk around each fitting and also added enough to plug the openings at the front and rear caused by the round fitting in oval holes. The caulk I used is stiff enough to fill the hole without collapsing into the hole and then sets up nice and firm. I tried to also smooth the transition from the trough to the opening to promote good drainage. I got a little sloppy with the caulk but got the job done. Everything will be hidden from view below the interior trim pieces so a little extra caulk to make sure the sealing job gets done won't hurt anything.
I SHOULD have done this job BEFORE I installed the slider window weatherstripping but it was fairly easy to work around it. I also did this job while the fixed side glass was out of the car which made the job a lot easier. I think it could be done with the glass in, but it would be a lot more difficult.
The remaining step is to cut and install on the barbed nipples lengths of hose which will reach to the drain locations. On the forward drains, I cut the hoses long enough to reach the drain holes and actually inserted the end of the tube into the drain hole in the bottom of the quater panel instead of just letting it drain generally into the quarter panel like the factory did. The drain hole at the base of the quarter simply drains into the interior of the rocker panel so if you really wanted to drain it all the way to the outside of the car you'd need to drill a hole in the lower section of the rocker and feed the tube all the way out. The rocker panels have existing drain holes at the front and rear, so the water will find them naturally even if you just terminate the tubes into the rockers. At the rear, holes already exist for the drain tubes just below the taillights and behind the bumper.