No, I had 3.73s and I switched them out for the 4.10s. You would need a dial indactor to see how much play you have in your rearend. The Zexel unit probably will be fine for you, the reason I chose the Eaton posi carrier was when we went to do the gear swap we found that the spyder gears were pretty messed up, so instead of buying new spyder gears I just went with the new carrier.
I bought all of these items from Summit 1-800-230-3030 or www.summitracing.com. I paid $193.95 for the Richmond 4.10 gears (part number RMG-4900091), I paid $95.95 for the Richmond Gear installation kit (part number RMG-8310441), I paid $439.95 for the Eaton Posi Performance Differential (part number ETN-19599-010). The S-10 rearend is a GM 10 bolt, 7 5/8 (7.625) ring gear, 28 spline. With the ring gear on the GM 10 bolt 7 5/8 (7.625) and 7 1/2 (7.5) are interchangable. Also for the installation you will need a bottle of GM Limited Slip Additive, and several bottles of non-synthetic gear oil.