Can a short block 350 engine be put into Chevy Astro van?

No, a short block 350 Chevy engine will not directly fit into a Chevy Astro van. While both are GM products, the Astro van originally came with much smaller engines (typically inline 6-cylinder or V6 engines). A 350 small-block is significantly larger and requires a different engine bay, mounts, and associated components (transmission, etc.) that aren't present in the Astro's design. The swap would be a very extensive and custom project, requiring significant fabrication and modifications.