For a slanty, the 2.66box is a bit of a chore with the hiway gears those cars typically have. The 2.66 works OK,until you load up the car to go camping.The 3.09 low gear is 3.09/2.66= 16.2% stronger which is the difference between 2.76s and 3.23s .
The 2.66 likes more performance oriented gears.....like up to 3.91/4.10s even, whereas the 3.09 is good down to about 3.55s/3.23s.
But when either box hits that second gear, she'll be wanting those 3.55s, for anything but a grocery-getter.
I sense you have a slanty A-body, and are looking for a little more oomph.
If an automatic, more stall goes a long way. I like a 2800 for that.
If a stick, you don't get the TM from the TC on the start-line, so your basic option is more rear gear, or a 3.09box.
But I don't advise the 3.09-od box by itself; second gear is way the heck out there. That second gear needs 3.73s just to stay even with 3.23s in the 2.66/3.09 direct 4th boxes. Criminy it's a long ways off.The OD box works well with 3.91s tho. First gear is a little deep, but they bring the second gear down to normal, and with overdrive the final-drive is down to 2.85, good for 65~2300/2400
My favorite combo is the 3.09box and 3.55s. It has plenty of starter gear, and if you stretch out first gear just a little more than you might consider normal, then it will still pull real good in second. If hiway NVH is not an issue, then 3.73s are pretty nice.
