I have owned my '64 Overlander since 1995, and at this point virtually every system has needed some kind of attention, and I don't think that my experience is terribly unusual. The remedies on my coach have included:
1.) Replaced the original Armstrong Bay Breeze Air Conditioner in 1997 after the compressor seized - - my dealer recommended this as he couldn't locate a replacement compressor of any type. The replacement is a Coleman Mach (13,500 BTU) - - downside is that it doesn't have a drain pan so condesate is deposited on the roof, and it is not thermostatically (wall mounted thermostat) controlled like the old Armstrong.
2.) Replaced the original furnace with a new Suburban unit (30,000 BTU) as the heat exchanger on the original had rusted out. This also necessitated a new exterior vent cover, but since the original had accident damage that didn't disturb me.
3.) Replaced the original Bowen water heater (10 gallon) with an Atwood (6 gallon) after the original tank sprang a leak. This required fabrication of a filler panel for the exterior coach as well as replacing the original vent shroud - - something that didn't distrub me as I always thought that the vent shroud looked out of place on such an aerodynamic shape.
4.) Installed new Dometic 3-Way RV Refrigerator to replace the apartment sized refrigerator installed by a previous ownerl. The 3-Way refrigerator supports running with propane turned off as the refrigerator functions superbly on 12-volt while underway.
5.) Replaced both roof vents with thermostatically controlled Fantastic Vents with rain sensors. This was a splurge, but is something that makes traveling with pets much more comfortable. In addition these vents make International Rallys more palletable except in the highest of humidity.
6.) Replaced the 12-volt electrical system with a Trace Inverter, 3 solar panels, electronic control panel, and three gel-cell batteries. This system allows me to go with out electric connections for a period of several days when air conditioning isn't required. AJL Solar handled this upgrade. Caravanning was a big reason that I took this path as I always worried about running short of battery power on the first two Vintage Airstream Club Caravans that I joined.
7.) Replaced the original PAR water pump with a new PAR pump as the original had too many problems to be rebuilt. The PAR is expensive and less readily available, but well worth the cost in my estimation.
8.) Replaced the original water tank with a custom tank sourced by my Airstream dealer. The original had sprung leaks along its seams resulting in wet floors if the tank was more than half full when the trailer was towed.
9.) Replaced the replacement toilet. The problem with this was that the previous owner really cobbled up the enclosure so the replacement posed something of a problem in obtaining an attractive end result.
10.) Replaced the original tongue jack with a new electric model. This was both a convenience move and a necessity as the original was displaying characteristics of stripped gears.
11.) Replaced original-style brakes with modern units facilitated by using "fully-loaded-backing plates". Since so many of the parts for the original brakes were either becoming obsolete or difficult to obtain that it seemed wiser to upgrade to the latest in modern equipment. In addition, all four drums were resurfaced and the shoes matched to their drums.
12.) Had damaged entrance door repaired. As with so many '60s coaches, my entrance door had blown open numerous times and required a significant amount of attention to produce a good seal.
13.) Replaced most of the window operators. These are becoming increasingly difficult to locate for some of the '60s coaches so I had my dealer replace any that were showing signs of wearing out.
14.) Replaced umbilical cord. This was preventative maintenance and in part was indicated because previous owners had made so many modifications that the existing cable just didn't seem sound.
15.) Replaced break-away switch. This again was normal maintenance.
16.) Professional restoration work included polishing and Plasticoat by P & S Trailer Service of Helena, Ohio; and interior refurbishment by Fowler Interiors of Symsonia, Kentucky.
17.) New Zip Dee awning to replace the original A & E Travel Awn 5000 that had damaged parts that were no longer available from A & E; and the repairs attempted resulted in an awning that was barely operable. While the coach was in for the main pation awning an awning was added over the bathroom window as well as one over the bedroom windows.
18.) Had rear end separation repaired as well as work on two outriggers. This was the result of having a rear bumper mounted spare tire for nearly 40 years (rear end seapartion). The issue with the outriggers wasn't as clear as they were the ones near the entry door and under the refrigerator.
At this point, my biggest remaining project is to have the axles replaced. My original axles are just barely within specifications so this must be done before making an extened journey with the coach.
With a Vintage Airstream, sometimes it is dfficult to draw a line between upgrades/mordernization, and what is required to keep the coach in safe, usable condition. I know that I tend to go a bit overboard with many projects as I know this coach will be with me for MANY years. I have a history with this coach dating back to when it was new and I was five years old.