Not sure when the 454 went out of production. Some where in the early 2000, I think. With that in mind, a used engine will have old gaskets that could possibly fail again. I wouldn't consider a used engine unless I intended on replacing all the gaskets, checking the valves and replacing the oil pump. With all the work it takes to R&R the engine, saving a few $$ is not productive. Then there is all the small items that will eat a hole in your budget. Hoses, belts, oil, filter, spark plugs, theromostat, water pump, power steering fluid, antifreeze, OH GEE! I think i need replace that too, etc. GRIN
And while I'm on a roll. That rubber air dam, above the radiator needs to be put back on. It's an important part of the engine cooling package. Now get out there and get dirty!
Richard