BuckHunter,
I am currently in the process of upgrading my 8 inch 2.79 open rear end to a 9 inch 3.89 locker on my 1965 mustang. I ordered the 9 inch housing from moser and the 3rd member off of ebay rebuilt. I did a bunch of research on this topic and i would recommend a gear ratio around 3.7. It is hard to find an 8 inch with those specs (especially a locker/posi) but the best place is to watch ebay for them. I asked the guy i work on my car with if it is easy to change of the ring and pinion gear (like you want to do to get a lower gear ratio) and he said it is pretty hard. So if you are going to keep the 8 inch housing i would recommend monitoring ebay as places like mustangs plus want a grand for the 3rd members. Below is a paragraph that i pulled from an article from mustangs plus and also the link that talks more about them:
"Now that we understand the meaning of a 2:80 open rear end verses a 4:11 Traction Lock rear end, let's take a look at how to choose what's right for you. Since the drive line in a 2:80 equipped car has to go around fewer times than the drive line in a 4:11 equipped car, the engines rpm's will be less at 60 miles an hour. The engine's rpm's with the 2:80 rear end and a standard transmission will be in the 2,300 range while the 4:11 equipped car will be around 3,500. Remember that the additional 1,200 rpm may not seem like much, but at freeway speeds will make the cars exhaust louder, create mor vibration, and use much more gas.
So why would anyone want a 4:11 rear end? The 2:80's are great for gas mileage, but not for performance. It takes far more effort from the engine to start a car rolling from a dead stop with the 2:80 gear ratio than it does with the 4:11. So, the 4:11's, while not the best for freeway driving, will make the car much faster off the line and through the gears, which is exactly what you want from a performance car."
https://www.mustangsplus.com/tech/axles/index.htm
Hope this helps
I am currently in the process of upgrading my 8 inch 2.79 open rear end to a 9 inch 3.89 locker on my 1965 mustang. I ordered the 9 inch housing from moser and the 3rd member off of ebay rebuilt. I did a bunch of research on this topic and i would recommend a gear ratio around 3.7. It is hard to find an 8 inch with those specs (especially a locker/posi) but the best place is to watch ebay for them. I asked the guy i work on my car with if it is easy to change of the ring and pinion gear (like you want to do to get a lower gear ratio) and he said it is pretty hard. So if you are going to keep the 8 inch housing i would recommend monitoring ebay as places like mustangs plus want a grand for the 3rd members. Below is a paragraph that i pulled from an article from mustangs plus and also the link that talks more about them:
"Now that we understand the meaning of a 2:80 open rear end verses a 4:11 Traction Lock rear end, let's take a look at how to choose what's right for you. Since the drive line in a 2:80 equipped car has to go around fewer times than the drive line in a 4:11 equipped car, the engines rpm's will be less at 60 miles an hour. The engine's rpm's with the 2:80 rear end and a standard transmission will be in the 2,300 range while the 4:11 equipped car will be around 3,500. Remember that the additional 1,200 rpm may not seem like much, but at freeway speeds will make the cars exhaust louder, create mor vibration, and use much more gas.
So why would anyone want a 4:11 rear end? The 2:80's are great for gas mileage, but not for performance. It takes far more effort from the engine to start a car rolling from a dead stop with the 2:80 gear ratio than it does with the 4:11. So, the 4:11's, while not the best for freeway driving, will make the car much faster off the line and through the gears, which is exactly what you want from a performance car."
https://www.mustangsplus.com/tech/axles/index.htm
Hope this helps
