I have replaced my 330 with a 425 in my 1964 F85. I'm going to be swapping in a bigger cam from Mark 230/234 @.50 lift is .480/.496 on a 110lsa. Engine is bored .030, 10.25:1 cr pistons, Hei distributer, msd ignition, roller rockers, performer intake, going with a 770 or 800 holley, long tube headers, 3in exhaust. I just got my th400 rebuilt and upgraded. I'm going to pick it up tonight. I need to get stall converter for it. I'm going through TSR racing for the converter. I'm running a 29" tall tire by 10" wide. I've been looking at putting in a ford 9" with 3.50 gears but have decided to look into just swapping the gears out of my 8.2 10 bolt also. It currently as the stock 2.78 rear end in it. What gear should I go with? Is it worth just swapping the gears or should I just swap the whole axle? The cars mostly on the street. Will only see the track a handful of times in the summer. I live about 6-7 miles from town so it does get driven on the highway. That's why I was thinking 3.50's I don't think I should go any higher with having to drive the highway? Quick performance sells the complete ford 9" for $2,300.

 

Hope you spent extra money for the N center...9" stock third members are the weak spot.
I am sure were going to get a TON of 9" lovers to say other wise...But they use stock used third members that have many years of people messing with them. We have seen many fail with pinion supports blowing right out the front of the third member. Because threads that have had bolt run in and out many times over the years ... plus the stock pinion support is too thin and small fractures are hard to see and appear good.
IF you are doing 9" do the NEW third member third member case pinion support and yoke.... Or do not do it.

10 bolt 8.2 can hold for what your doing the ratios 3.36 or 3.55 can be used. IF you are doing more freeway 3.36 will be a good gear...BUT sounds like you will have BIG tires so 3.55 will be fine too.
You need to figure out what RPM is a good drive able area for your personal needs.

Both rears will have bolt in axles - so you need not worry about ruin rear quarters if they do snap.
I think the choice is how much time you will spend at the track will determine the choice.
If the originality of your car means more then go with the 8.2 rear...they are harder to find these days only 2 years 64 65...66 they started widening the rears to 55.25
If you decide to do the 8.2 shoot me a PM and will price you out some parts.
Jim
JD Race