On the 460 keep an eye out for the back passenger side exhaust header bolt being broken off, and the calipers. Make sure you're happy with the braking power and ride of that rig (I never was.)
IMO Four Winds has a bad reputation for quality. Never owned one, but seen a few that were falling apart.
On Edit:
I read a few of your prior posts. Things I learnt or at least feel when it comes to mileage. Ford v8's will have low miles because they are hard to drive. From that era will have 40-65K miles on them. GM v8's from that era will have about 100K miles on them since they drive easier. They will have problems but their owners are loyal. The ford v10 is really what you want. It is a commercial engine and will go a very long way. I'm guessing 200K and from the miles some are racking up, they must drive OK.
