I plan to do a 73-76 disc swap and I have a set of 4.5" rims and tires. I'm thinking I could get a donor car and take the rear as well. I have a few questions:
1. Does front discs mean 4.5" bolt pattern? (Any disc cars with 4" bolt pattern)
2. What rear should I use? I have a 64 Dart with a non OD 4 speed. I have a 4 bbl with a 252 Comp cam and the car is mostly street. It has a 7 1/4 (3.23) in it now.
3. Is a 8 1/4 or 8 3/4 from a 73-76 A body a direct bolt in or do I have to move (weld) the mounts? What about the length?
4. Is it possible or practical to have a non-slip changed to a posi or is it better to "go fishing" for a used one?

I have read that the 7 1/4 isn't that bad for street and I think I can change the axles (to 4.5") and drums (to 10").
Thanks for your answers/experience

_________________
"Nothing in all creation is hidden from God's sight. Everything is uncovered and laid bare before the eyes of Him to whom we must give account."

Let's start with some simple ones....

7 1/4 rear is a good rear for what it was designed for, and some guys here have done really well with them for 'other' uses... You can't swap the axles from a 1973-1976 rear to the pre-72 rear...axle lengths were different (housing and axle tubes changed too...).

Good news! You can bolt in any A-body rear axle and it'll fit right in!
So you can try to find a 1966-1972 A-body 8 3/4" axle and swap out the 4" bolt pattern shafts for 4.5"( or 'large bolt pattern') shafts. Or you can swap in the 8 1/4" if your donor disc brake car had one. Both of these axles are getting harder to find and the 8 3/4" being more desired will be more $$$, than the 8 1/4"...The 8 1/4" will be easier in junkyards to find used gears and sure-grips for (Dodge Ram pickups with the 8 1/4" or 8 3/8" 10 bolt cover rear always have some god 3.55 or 3.91 tow package gears to work with if on a budget and you have the time and tools...)

If you really want to wake up your car, the sure grip will come in handy (it sure helped out lots last winter during a snow storm when I had to get to work and had no snow tires...kinda funny how a Duster can whip past those Grand Cherokees and Suburbans when you know how to use/drive your vehicle....)

Other things to ponder when 'scheme-ing' up a plan..if you're stuck with the 7 1/4 from the other car you can have a shop put the 3.23's from your rear into the donor rear for some $$$ (I'd take the 3.23's over say, a set of 2.76's any day...), if you have a junkyard with a 'boat' (like a 1966-1974) Imperial, or New Yorker with the 8 3/4" an axle shop can cut the rear down and respline the axle shafts for your needs. Also depending on supply and demand, you can also shop for a Ford 9" rear and have it 'resized' to your needs too...

If you do go for the 7 1/4" keep your eyes peeled in parts for sale ads, and on E-bay sometimes the 'rare' 7 1/4" sure grip unit shows up and that will help your launches too...

Hope that gives you plenty of 'options' to play with/ shop for/ save your P's and Q's to do...

-D.Idiot

No to #1. Disc brakes for 72 and earlier cars were 4" bolt pattern. Also known as the kelsey-hayes setup. If you currently have a 72 and earlier car with 9" brakes then interms of front end work the only things you'll need are lower ball joints (availible from local parts stores) and spindles (getting harder to find but still out there).

I swapped to the KH sbp discs up front on my 71 (vs the 73-76 setup) for a few reasons... I didn't want to swap rims, and I already had a sbp 8 3/4" from a 72 A body and didn't want to change/redrill axles.

Hey thanks for the info!
If I find a 8 1/4 from a Ram pick up, will it be too big (wide) for my Dart?

_________________
"Nothing in all creation is hidden from God's sight. Everything is uncovered and laid bare before the eyes of Him to whom we must give account."

They will be very wide, and these can't be 'chopped down' like the 8 3/4"...

You need an axle assembly that measures 51.4 to 53.2" from backing plate to backing plate....for the perfect fit...you can use wider ones, but have to move the spring perches, and get properly off set rims to fit...

-D.Idiot