If it helps I'm now waiting for a VIC (Vehicle Identity Check) on my 924S which was written off as Category C earlier this year.
Basically if you go through the insurance route you willl get quotes to return the car to original condition including all new panels, labour charges for all the dismantling, repairing and putting back together. In the case of a 924 (or 924S or early 944) which isn't particularly valuable it doesn't take much damage to write one off.
So I bought mine off the inurance company and have repaired it. Currently my log book has been returned to DVLA and I won't get it back without having the vehicle inspected. As I understand it this is an identity check, not a check on the quality of repairs. It seems to be mainly designed to catch the 'ringers' who try welding 2 halves together to put a car back on the road. As mine was only panel damage I have no concerns over passing that check. Indeed with the bits of re-spraying I have had done my car looks better cosmetically than it ever did before the crash ! I haven't replaced every panel, some I've repaired and some I've replaced with second-hand ones - but you have to remember the rest of my car is 18 years old an never was a concours one, but it is very presentable and not one to be ashamed of. I do have a record of the exact damage and can point to all the parts that have been replaced and the receipts for the bits. Photographic record will count for a lot, I believe, at re-sale time to demonstrate what really happened and what was done.
I can still use it (it's insured third-party only, although VOSA, the people who run the inspections) advise me that an insurance company should not put restrictions on the cover during this period. It is still taxed, but obviously without a V5 I won't be able to re-tax it - fortunately for me mine had abour 9 months tax remaining at the time of the incident.
I think the insurance co will want a fresh MOT as well as the confirmation of VIC. Having passed the VIC I can re-apply for the V5 which comes marked as having been "Cat C written off and inspected on DD-MM-YYYY", or something along those lines.
So in my case, I was in the accident, I know the full extent of the damage, I bought and repaired the car at a price that will not be outrageous should it's value be reduced by the stigma of Cat C. These cars don't have a huge value to start with so you can't lose a lot. The alternative for me was to take the money (again, it doesn't amount to a lot) and look for another car. The problem there was that I am not in a position to add any other funds to the payout just yet, hence I'd have been gambling on finding something similar with no known history, whereas I had a car which during my ownership I had gathered enough information and data to konw it had a very sound engine, good running gear, no bad rust etc etc. There was a lot of comfort in knowing the base car was what I wanted and a sound vehicle. So, weighing up the fact that a loss in value didn't amount to much in real terms I stuck with my car.
In your position you need to satisfy yourself that the owner re-built it for similar plausible reasons. You need to be sure of the extent of panel damage and the quality of repairs. These cars are pretty strong and, as my experience shows, can be written off for what is fairly minor damage, but I've no doubt there are some bad ones around too.
I am aware the value of mine will be affected, to what extent I don't know. I do know that it's value is unlikely to fall below the salvage/repair costs though, so I can live with that, especially when weighed against the knoweldge that the rest of the car is fundamentally very good with all the usual problems having been addressed in recent years.
Have a look at
this
best of luck........ Phil