Use car parts are fine to use if you are like me! I like every thing new. Don’t worry use parts in this manner are just fine. The only thing I would do is put white lube on your window track and door lock linkages. The only thing I wouldn’t use is the plastic clips if you cant get them.
For brake booster rebuilds, the two with the best reputation are “Booster Dewey” and “Karps”. Karps is the one I use. If you are looking for a source of rebuilding kits, I’m not going to be able to help you, as I’ve not run into a source for them. If you are a member of a club, post your question on there web site; someone will have an answer for you. WPC is the main Chrysler club, as you probably know, but I’m sure there is a 300 club also.
Some vendors advertise new heater cores on eBay all the time, so I’d look there first. I tried that on my 67 Imperial, and they couldn’t help me. But I’ve found that a good radiator shop can rebuild and even rescore any heater core I’ve ever had to repair. I have gotten rebuilt power brake boosters for 64 Chryslers from AutoZone and from NAPA in the past – they are another source at around $100 exchange.
I can tell you my experience, I use Silicon Grease, and available at most auto parts places as it is designed for this purpose. It is clear grease in a tube, with a consistency similar to that of Vaseline, but without any petroleum content, so it will not attack the rubber or any plastic you put it on – it is totally inert in that respect.
It is used in space instruments for this exact reason and I’ve always used it on my cars -it keeps the weather-striping and rubber bumpers under the hood etc. just like new. I put it on in a thin coat with my fingers, rub it in a bit, and then wipe off any excess that might come in contact with someone’s clothing. GE makes it,used auto parts and so does Dow-Corning. The DC part number is DC-4. I got my last tube from the NAPA store – it was the GE brand, but it is just the same to use and the way it works.
I have a 1996 Jetta Trek with a door lock problem. The locking mechanism fails to actuate any doors other than the one in which I actually use a key. And, after using the key, I heard the vacuum pump running too long, as well as the telltale hissing which revealed a leak under the dash on the d/s. This all seemed to happen after I had a stereo system installed.