Hello, I don't know the exact dimensions of the engine compartment in a 1990's -early 2000's Chevy Astro or how close it is to a Chevy S-10 of the same years. So I don't know if a 4BT could be swaped into one or not.
Are you talking the rear wheel drive or all wheel drive van? A 4bt is a big, heavy engine. Around 750 lbs or more. Probably take some serious frame and suspension upgrade. You can put a 4bt into a lot of vehicles but might not always be the best idea.