Rebuilt 340 been sitting for about 5 years

Hi R.S.D, my rebuilt 340 has sat without running for 20 years, if one keeps a consistent regiment with priming the engine and turning the engine manually from the lower crank and squirting oil down the spark plug holes, then it doesn't matter how long it sits. The engine should be fine when it comes to finally running it. If you have not done any of these things I've mentioned in 5 years, you will need to investigate those areas the others have suggested. If you prime it and throw a little oil in the cylinders and are not able to turn it manually with some force then its probably seized.