An O-300 172 (or 170 for that matter) makes a GREAT two place airplane - if that's your mission.
We've flown '81D, an O-300 170B with a climb prop, for 5 year (just sold her).
On the east coast, where the worst density altitude I've ever seen is 3,000 feet, she did wonderfully with my wife and I and a few bags.
Having said that, We're putting a TCM IO-360 in '95D.
As someone has mentioned earlier, some parts for the O-300 are becoming tough to find but it's mostly the C-145 parts. Namely the sump and the crank.
The sumps are rotting out from water sitting in them. They look fine from the outside but are rotting from the inside. They are difficult to repair in an approved way. The 8 bolt C-145 cranks don't seem to exist anymore. The six bolters are still around and can be bought from TCM for about 5 large as it's the same as the TCM IO-360 crank.
As an East coast two person low lands airplane, a straight tail 172 is tough to beat in price and performance.
Really sorry to hear about your plane. It looks like you really took care of her and cleaned her up nice.
Best of luck finding the next one to do the same.

