I have a 86 s-10 I recently changed my old 350 witch was bone stock,for a newly rebuilt 350 dyno'd at 340hp.My truck came with a 4-cylinder and I love the gear ratio that came with but with the addition of some good tire and traction bars this winter I'm afraid the stock rear end might not hold up.I'm looking an affortable fix that will hold up after my truck starts to hook up any sugestions  

First thing would be to try and find a rear out of a later model 4x4 S-10. Usually the 4x4 rears were a little beefier.

The other option is, a 8.5" 10-bolt out of a 68-up Nova is about the right width for your S-10, that could also be a possibility.

The third option is, check the rear end companies, someone probably makes a drop-in housing for S-10s to solve this problem.  

I put 700 hp thru a 8.5 with 28 spline axles,at the track,on slix,puttin air under the front tires,pushing 3400 lbsOn an 8" slick,too(just bragging now).Had no problems.You won't need to spend alot of money.Probably just beef what you got.What rear do you have now?  

I have run a 325hp/400lb-ft  355 in front of a TH350 with a shift kit through a bone stock 7.5" S-10 rearend for about 10 years with no problems.  That inlcudes several strip passes, multiple street races, countless burnouts, and hauling up to 1,300lbs of gravel.  Runs 8.7's in the 1/8th.  The rearend is a 3.42 that was originally behind a 2.8 v6 and manual 4 speed.  Don't spend any money you don't have to, your stock rearend may just impress you.