[D13]

Up to 93 MAY be cable. 91 up were electronic speedo. Also came in cars. 87 up had many improvements, cases with a K cast in are considered the best.
Unles you rebuild these yourself, it might be easiest to pick up a cmplete unit from TCI/Monster/Phoenix etc. Any used one is pretty much a crap shoot. Most have been rebuilt at some point in their life (remeber these are 20 years old!) and it's hard to tell what internals they may have. Stay away from V6 units (less torque capability) and be aware that 2.8 S10 units have a different bell housing that doesn't bolt up, 2wd and 4wd have same cases but different outputs.
Trans also came in Caprices, in 350 powered cop cars in the 80's and all once they went to the round body. Also Vettes and Camaros.