No OBD-II connecter? Strange!
Apparently GM did all sorts of crazy things back then...I've been doing lots of research and it seems that there are some S-10s with the OBD-II connector that are NOT OBD-II, some without the OBD-II connecter at all, and some that are true OBD-II.
Apparently the way to find out is look at the connector under the dash and see if pin 2 is populated, and 10 is empty. If this is true, apparently it's OBD-II. Mine is. Also, under the hood, on one of the emissions labels, in the bottom right corner it says in very small print "OBD-II certified".
Here's a good thread on the subject....
http://www.obdii.com/ubb/Forum2/HTML/000250.html
Mine is an early build '95 Blazer LT, built in 11/04, and it's OBD-II....
After sending 5 emails back and forth to the guys at autotap, I think it'll work!