From what I've learned listening to experts and limited experience, there is a whole range factors that define what is "restorable" condition. You might consider such things as:
- Is the restored piece (car, caboose, loco) to be operable, even on a limited basis so that structural integrity and safety matter, or will the piece go on static display so that a cosmetic rebuild is ok?
- Is the goal to retain/reuse as much historic fabric as possible, within the purpose of the restoration, or build a replication with new material using the original as pattern?
- How rare is the piece in the population of historic RR equipment?
- What is the structural condition and quality of the existing material? (if retaining fabric is important)
- How complete is the piece? It get's harder to realistically restore if too much is just missing.
- On a practical basis what resources might be available?
- and others.
As said above and elsewhere - with enough $$ anything can be rebuilt/recreated/restored. The trick is establishing priorities.
IMHO - the primary structural factor for a wood-frame era car as in the OP that decides between a) it's possible to try and restore what's there versus b) a complete ground-up replication, is the condition of the large wood frame sills. If those are significantly rotted, or worse, cracked through vertically, then those must be replaced with all new timbers. So - the piece must be 100% disassembled, and rebuilt frame up. From that point, you see if it's worth it to save what else is there one piece at a time!
I once had the privilege of being on a docent-lead walk through of the storage barn at Nevada St RR Museum. At the time, this was not public territory. After saying how impressed we were with the number and variety of equipment (mostly rare, wood-frame era passenger cars) we asked about restorations. Basically, we were told the policy is that the cars were to be only preserved as-is as long as they lasted indoors. The cars were available for research by historians/authors, but were otherwise not going to be "restored". This is, to me, the archeologist view - a museum is to hold articles in as-found condition to be preserved for study, but to rebuild/restore will inevitably change them and reduce their value as unaltered historic records (Analogy - what is lost if an authentic partial dinosaur skeleton is "restored" back to a life-like model of a dinosaur).
A very experienced docent at a museum on the east coast once told me that their "restoration" policy tried to look objectively at the rarity of a piece based on 3 categories:
- "Last-of-Its-Kind": saving it is a prioity, make an attempt for at least cosmetic restoration.
- "One of a Remaining Few, or Other(s) Already Restored": probably maintain in "arrested decay", and make restoration a lower priority.
- "Fair Number Still in Existence and Restored": probably favor no action, other than retaining the piece on the property.
This reflects the reasonable view, "we can't afford to save/restore everything". However, it also provides a thought-out method of decision making and prioritizing.
Bob of AZ