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...yeah. $350 is way too much money to spend on a donor bike. Look for something that has dry rotted tyres and needs a new chain and a lot of work. You're going to take it apart anyway, to do the transplants, so you do the mechanical work, cleaning, relubrication at the same time you do the swaps. It opens up a lot of bargains, because you no longer have to pay attention to the frame size of the bike you're using for parts.
I've done this with PX-10, an early Ironman, and a Motobecane Grand Record. It was the only way I could get those bikes in my preferred 24" frame size. For some reason, most of the American importers just imported and sold the 23" and the 25" frames on those two French bikes. The PX-10 frame came from a guy who bought it in Germany, and he rode it so much all the components were pretty well shot.