Does anyone know if it is possible to convert the rear whhels and front wheels of a 1994 s-10 blazer with electronic 4 wheel drive switch to manual lock-outs.  Will it correct the limited slip not working in the rear?  

im not aware of a kit for the front or rear wheels and are you sure you have a lsd in the rear?  

Changing to manual locking hubs would have absolutely no effect to the function of of an open or limited slip differential. 

And no, you cannot add manual hubs to the front of your current truck, as your vehicle has IFS and "Central Axle Disconnect" to engage the front drive wheels as versuses locking hubs. 

Your truck probably doesn't even have posi, or lsd.

All the important stuff has been stated, and you will never find anyhitng of that sort for the rear, or front for that matter!