All great tips above, but it's weird that it works well initially.
Just a guess as we don't have real cold conditions much here, but could it be that the heater going cold is related to the engine getting properly warm then the thermostat...
I recently lubricated my driver’s window regulator and it made a huge difference in the smoothness and speed of the power window. I used a spray silicone on the regulator pivots and a dab of grease on the little plastic rollers. The passenger...
They are in the door.
This is a picture of mine.
I could extend its life by disassembling it, cleaning the carbon buildup and reassembling it.
I am afraid I do not have pictures of the disassembly and clean up.
Keep in mind 70 series axles are quite narrow. Tippy enough std. If going to the trouble of re-making spring mounts etc etc for SOA it would be worth checking if axles from something wider could be used.