If it is out of a bucket truck then it is probably a Tall Deck 427... you can make these into a 600 cube monster. In stock form they don't like high RPM's very much, pistons have an extra ring, and standard big blocks stuff (most brackets, intake, etc...) will not work on them. Lots of drag racers and boat racers build the Tall Decks... but they put alot of $$ in them.
Also, make sure it is NOT a 366... they look like a 427 but are a sh!t motor, and not good for anything.