My 74 SS has a limited slip tag on the rear. Any idea what these can handle power wise? I've got a 400 sb and a th400 to work with.

If it's in good shape, I would think you'd be OK with it up to 400hp easy depending on how your car hooks up.

goo I was hoping to shoot for that power range. any common ways to help a 4th gen hook up? traction bars? sub frames?

Its currently got 255 70 R15 tires under the back end now.

There was a recent article in Super Chevy or Chevy High Performance (Hot Rod?) in which they overhauled and upgraded a 10 bolt 7.5" rear diff. They said it would be ok for over 400hp so you shouldn't have a problem with the 8.5" you have.

worst case I guess is changing out the gear ratio if I need to for better acceleration. Any idea what the stock limited slip gear ratio is? I would think it might be a little better than the 2.78 or whatever the open axles usually have.

I have 3.08's. Not bad off the line and great on the top end.

Most likely 2.43 or 2.73.

I'm not a 4th Gen kind of guy, so I'm not sure who makes aftermarket upper (adjustable) and lower contol arms with polygraphite bushings for 4th Gens, but I am sure as with 5th Gen Elkys this would be a big improvement if you replace the OEM arms. Add a sway bar if you don't have one, a set of quality shocks like KYB gas shocks, and possibly some Airlift airbags (independently valved to offset pressure). Then you need to decide on the tire/wheel combo. 255's are good, but consider BFG street drag radials, tire compound and tread pattern makes a difference. If aftermarket contol arms are unavailable, or too costly, you might consider boxing the OEM control arms. Seek out other 4th Gen owners and see what does or doesn't work for them.

My '76 Sprint has a '70 Buick 455 that was factory "rated" at 370 hp and 510 ft-lbs of torque. The previous owner of this blew up the original 2.56 8.5" rear doing burnouts. :? What let loose in the rear end is the crosspin that holds the spider gears in place sheared where the bolt holds it in place and bent at the top end of the carrier, effectively releasing the spider gears to roam freely around and cause all sorts of damage. I have 255/60/15's on the rear right now, and it is not nearly enough tire for the wheel well. You can easily fit a 28x12.50x15 M/T ET Drag with no mods. If you go with ET Streets you can fit a 28x13.50x15. Or if you go with street tires you can fit a 315 series tire. You could fit a 325 series if you bent the wheel well lip flush. Of course rim width and backspacing will play a major part in fitting a large tire.

Charles