Whizzerick,
At that price, I say go for it. I paid $275.00 for a '54 261 that was in dire need of a rebuild. Nonetheless, after the rebuild I am very happy with the results.
Since '57 261 you are considering came from a car and most likely has a fiber cam shaft gear, you may want consider replacing the timing gears with a new gear set containing an aluminum cam gear. The aluminum gear will make more noise; however, it much more durable that its fiber counterpart.
Good Luck. I am glad to hear of your find.
