Found a 440 Motor

400 dollar chance without hearing it run with mufflers on it, or otherwise open manifolds or flip it upside down, pull the pan and try to inspect a few rod bearings, crank bearings and (is it possible to mic the cylinders from bottom?). I usually spend at least 30 minutes talking to the seller, observing their operation, making observations and decisions about their character and the legitimacy of their "claimed status" of a part to be sold, particularly when you cannot dig into it and determine its nature for your self.

If they are too good to spend a bit of time and explanation about the item and are "take it or leave it because I got others ready to buy so stop wasting my time" type of behavior, then I will leave it.

If it is legitimately a good quality stock or mild setup without major issues then it's a good price for sure.