68 rear ends?

you probably have a c-4 tranny and an 8inch rear. u need to post pics of the pan on the tranny and the bottom of your rear carrier for us to tell u 4 sure.

You probably have a C4 being that it is a '68.

I currently have 2.80's and I'm looking to change to 3.25 or 3.5. I have a 9" rear in my '68 coupe, but mine is decidedly rare. Chances are that you have 8" rear. (Mine was definitely swapped by a previous owner since it is not even a '68 9".)

Look at the back of the axle, is it smooth (no buldges? Is there a drain port is the lower right hand quadrant (looking aft forward)? If so are the ends of the axle tapered or straight? If straight then it is probably a 9" if tapered then probably 8". Now if it has a bulge in it, then it is most likely a 9". If it is smooth with no tapered axles, and no drain port, then it is probably and 8".

I would almost be willing to place money on you having an 8".

There's an easier way to tell an 8" from a 9"------- if you can remove the two bottom carrier nuts with a socket and ratchet, it's an 8". If you have to use an end wrench to remove them, it's a 9". I would also make sure the transmission is shifting into 3rd gear before swapping rear gears.

I think you have low gears. The bigger the number, the lower the gears. I'd go with somwhere under 3.50.