What do you guys recommend I do to the engine before I install it?
Depends...was it running when it came into your hands? If so, tell us about that...anything specific you may have noted...
If not, have a competent mechanic or machinist examine it...a professional can spot telltale signs of problems which might escape the casual observer.
Unless someone was dumping sand down the breather holes, I'd just leave things be and let the engine oil suspend the stuff and trap it. I've seen some god-awful glick in high mileage engines and they continue to run just fine.
I've found, in my years of doing hydraulic work, that I can actually make the stuff dirtier when trying to clean it. I just trade one type of debris for another. As was mentioned, the only way to really clean everything is to disassemble and clean in a pressure tank with a clean-water rinse and then bag until assembly.
Have fun!