Actually, if the brown rust is coming from between the strands it can indicate a serious problem with the
rigging IIRC. Stainless steel is just that... stain less...not stain free... and it will rust, especially if it is either deprived of oxygen or exposed to certain chemicals.
If the
rigging is swaged, then I would definitely want to closely inspect the lower swages as they are the ones that tend to fail first.
Re-doing the running
rigging isn't much of a problem...just a pain in the butt.
Major differences between CNG, which is primarily methane, and Propane is that CNG is lighter than air, and doesn't require the same ventilation of the gas locker that Propane does. Also, the pressure that the gas is used at is different, as is the volume used. Propane has a much higher energy density IIRC.
Why do you want a power
winch?? It might make more sense to get a manual
winch that is large enough to handle whatever it is that you want. The installation of an electric
winch requires you to run electrical wiring, and to make fairly large holes in the deck to accommodate the
winch motor.
As for heaters... it would be best to get a heater that uses one of the
fuels you already have aboard...either propane, since you'll be converting the galley to propane, or diesel. They have about the same energy density as heating
fuels go. Personally, I would go with a diesel heater, rather than a propane one.