Honestly, a junkyard 8.8 is perfect for what you're describing - if you've got the skills to fab it...

 

No fabbing necessary, already has a gm 8.5. Turbo buick guys run single digits on that same axle. Pick out what gears and diff you want.

 

On a related note, can you fit an 8.625" carrier in an 8.5" housing? Are they like some other rear ends I've seen where the housing is different depending on final drive ratio? I seem to remember some rears were made with like 2.xx ratios and some with 3.xx ration and you couldn't swap a 3.xx ratio carrier into a 2.xx housing. But I could be wrong.

Jay

 

Yes you can replace the guts of the rearend and you have a lot of options. The stock carrier is probably an "open" differential, meaning it will spin one tire if you floor it. Depending on your goals, you might want to replace it with either a limited slip "posi" or a gear-type such as a tru-trac. I would stick to Eaton personally. The carrier itself must be replaced if you plan to increase spline count, but in your case I would stick to the stock spline count since you really don't have enough power to warrant an upgrade. If you want to upgrade the axles, you can get aftermarket axles that use a stronger material and heat treat. Strange, Moser, and others offer these. C-clips are fine for this application. I used custom Strange axles on my Nova and I was very happy with their customer service and quality of the product, but I have also heard good things about other companies. For what it's worth, mine are Strange 30spline street/strip axles. I eliminated c-clips on mine and upgraded to Ford bearings, but I autocross my car and I have more power than you're planning on. I also changed to disc brakes in the rear I did not want to worry about pad knockback which can be an issue if you are autocross or tracking the car with c-clips and discs.

For bearings and seals, you will want new carrier and pinion bearings, new pinion seal, new axle seals, and diff cover gasket. When you buy new gears you can get an installation kit that will usually come with all the pinion and carrier related bearings and seals, but it will not come with axle bearings and seals. Use Timkin bearings - don't skimp in this area. Find a good differential shop and they can advise you on how to build for this power level - you don't need much.

Consider upgrading to a cast aluminum diff cover - they are more reliable at sealing and some offer carrier support. Also think about whether you want to upgrade to 1350 u-joints - if so you would likely need a new yoke and corresponding bits for the driveshaft. I don't think this is necessary at your power level. If the car has 1310 or 1330 u-joints those are probably fine. For what it's worth I am running 1310s on my Nova.

 

There are definitely carrier bearings to do the opposite - 8.5 carrier in 8.625 housing.

The 8.5 10 bolts have a 3 series carrier on 2.73 and higher numerical carriers, if memory serves.