If you're serious about a Small block V8 into an S-10, then you should visit this site:

www.v8s10.org

Everything you need to know about the swap is on this site. The 89 S-10 usually has a rear ratio of either 3.08, or 3.42. That is the favorite ratio for highway speeds. The simplest way to go is a small block Chevy with special engine mounts from JTR. hooked up to a TH700 4R trans. The whole thing is a bolt-in and you can use the existing driveshaft without altering it. The whole process is explained within the posts at the above site. If you want to use another make of engine and trans, that's covered in there too.