83 Camaro 454 project. which 454's are junk ??

[86TransAm]

My nephew and I are just starting a 454 83 Camaro build. Caper150 and I just towed the car to my house a couple days ago.I have seen several 454's for sale but one thing I am unsure of is are there some motors to stay away from ???one guy has one in Owatonna that is seized up, kinda makes me a little nervous.another guy has one out of a 91 school bus.
the intended use is the build it to 496,and make it streetable. nothing to wild but nothing to mild either.Jason (my nephew) wants a nice car to be able to take to car show and I am sure he would like to show of its power a bit lol.this motor would be carbed and 100% natural aspirated,no power adders.just something very fun and reliable.Jason is over in Iraq right now so I am kind of his gopher.


so what castings should I steer clear of?? thanks in advance for any input you guys may have.