Brand New 350" Crate engines start at around $1600 (with a warranty) so look at what you're buying pretty hard . . .
I'd do a "Wet" leakdown on it at least, before I handed over the whole wad of cash . . That and get a pretty good reason for selling it from the seller . .
"Buy when someone HAS to sell, and sell when someone HAS to buy" . . .
"Want" is a lot different than "Need" . . .
Just advice from an old geezer . . .