My 68 has a 10 bolt.

I'm building the motor with mild bolt on's (double hump heads, 268 cam, air gap, 600 cfm and a HEI), hopefully will get close to 400 hp.

How hard is it to change the gears?

Suggestions on which gears?

3:73?

10 bolts are strong, 12 bolt is stronger, If you re gonna spend money , why not go in the right direction.

If I keep the 10 bolt, how difficult (can you) is it to change the gears?

Any suggestions on a ratio based off of the configuration above?

alot of other things come to mind like auto or stick. doing racing or driving it on long runs.i dont think you will get 400 hp.but also depends on compression ratio. valves.600 carb is too small for a 400 hp motor.

I dearly love my 12-bolt's old 3.31's so a 10-bolt will use 3.36's if not mistaken!!

And I would not go any lower than 3.73's unless I wasn't gonna drive her hardly at all!!

pdq67

The rear end should be the 8.2 10 bolt, unless it has been changed. The 3.36 would be a good gear if it will be driven on the highway any. The 3.55 is a good gear for mostly in town driving. The 3.73 is a little more hard core and not very good for highway use.

I recommend an Eaton posi and after market axles for the 8.2 rear end. Installing gears requires a few special tools and a LOT of patients. It requires assembling and disassembling the whole rear end several times to get the pinion depth right. You will need a dial indicator with a magnetic base, a press with a bearing seperator and a few other tools. A good installation kit is required if you want things to go smoothly. Get quality parts. Don't try to save a few dollars on cheap parts.

What trans do you have? If you have an overdrive its a whole different ball game...

I have to ask the same question 400 bird is asking. What tranny? I have quite a bit of on the road experience with Hot Rods and Classics. For the average Joe 4.10/4.11 is a 'forget it'. 3.73 with a 700R is perfect (IMO). 3.55 is a good choice for a TH350 or TH400. The type of driving I am referring to is the hot rod signal light to signal light driving, and not driving to Balitmore.

Big Gear head is a local board expert. I have only put gears in one GM rear end, and won't do it again.

FWIW - The Camaro I am (re)building has a 491hp motor with (now) a TH350 (later a 700r or 200r). I am putting a Ford 9" in it with 3.70 gears.

Good Luck!

I have the original 350 turbo. I'm going to have it rebuilt.

I think based on the above, I may have a pro rebuild the rear and install 3:55's.

But the bottom line seems to be that the 10 bolt is a good rear.

I have 3.73's and 27.5" tall tires which runs 3000ish @ 65mph.
Buddy with 3.55's and 26" tall tires runs 3000ish @ 65mph also.

Look at what tires you're running or plan to run and then decide.