The perfect donor would have a rock-solid engine, transmission, cooling system, chassis and steering, good enough body, but with worn out shocks, failed cats, bald tires, and a crappy convertible top, rear window, and interior to lower the price.
12K miles is very odd. I would wonder what the story is. Has it sat for years unmaintained, and what does that mean? The transmission alone is worth good money since it has basically no miles on it! (Junkyard transmissions with lots of miles go for $500 and up.) The engine with basically 1 year of driving on it is very appealing but then it also means if it has a serious problem it may be too soon to know.
The key thing is the engine, chassis, and steering. You would always refresh the engine (IMS RMS fixes) but everything else you want to be good to go. Things in the wheel wells (calipers, hubs, uprights) are not a big deal to replace but you'd prefer them to be OK to begin with.