There are always a few A-Body (5 on 4 inch bolt pattern) 8 3/4 units on ebag... search: mopar 8 3 4 a

The trouble with the 8 3/4 swap is that it becomes expensive... that is why many look for A-Body 8 1/4 units or change lug patterns, then use the F@rd 8 inch.

What is wrong with the 7 1/4 you currently have??
DD

Nothing is wrong with my current rear, but I am looking to beef up the compression on the slant 6 or swap out eventually for a 318 or something with more ummmfff. I figure that if I get a more powerful power plant, I will need to bump up to an 8 1/4, no?

The 7¼ has a somewhat undeserved bad rap. The hotest Mopar put in front of it was the 273HP with a 904 auto. 273 HPs with 4 spds got the 8.75.

IMO, a master plan for how you're going to develop the car is essential. There are other options on the rear if, for instance, you're going to put a BBP disk brake set-up under the front end.

If you plan to drag race the car, you might want to re-consider using a C-clip rear end (that takes out both the 7¼ and the 8¼).

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You can't fix stupid. - Ron White

Actually in '65 the HP273 with a 4-speed was still backed by the 7 1/4. Also, most of our 7 1/4s have bolt in axles, not C-clip.

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Joshua

I agree, as long as it is a sure grip. I am running a 3.91 SG 7 1/4 rear with slicks and 358 ft/lbs torque.

But, Eugene, in your case, I think I would keep my eyes open for a 8 inch Ford rear, or an "A" body 8 1/4, and change the front to large bolt pattern.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Yes, for now I am going to keep looking for a 8 1/4. I am a little intimidated by the Ford 8 inch. It is not a perfect bolt in, plus I am not sure what Ford year would be the best match for my cuda...looks like I am going to keep looking at ebay from what everyone is saying...

Couple of months ago I bought a 73 or 74 A Body 8.25 that I may end up selling (unless another A Body comes along). I wouldn't be using it in my other A Bodies since I have 8.75s for them! The PO disassembled it for inspection and cleaned and painted the housing black. He ran into some money issues so I bought it. I was going to use it in my 65 Valiant convertible; however, I found the the Valiant has several severe cases of underbody cancer. If any interest let me know.

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65 Dart station wagon slant 6 - now under construction
47 Dodge Custom 4 Door sedan
87 D100 Short Bed slant 6

Retired USAF 1966-1986
Retired US Postal Service 2004-2014

Would it be a straightforward bolt on or would I have to do any tricks? Do you happen to know?

Other than reassembling it, it's a straight bolt in affair to the A Body.

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65 Dart station wagon slant 6 - now under construction
47 Dodge Custom 4 Door sedan
87 D100 Short Bed slant 6

Retired USAF 1966-1986
Retired US Postal Service 2004-2014

Installing a "A" Body 8 1/4 rear into a "A" body that had a 7 1/4 rear, will require the correct shock plates and "U" bolts, as the axle tube is larger. Will also require a shorter drive shaft. I don't know about the park brake cables. But yes it is almost a straight bolt in.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

How much are you going to build the slant? Are you having problems with the 7-1/4"?
If I was going to the trouble of changing out, I'd go straight to the 8-3/4". There would have to be a pretty good reason to do so behind an automatic transmission slant six.
Sure, you can scatter a 7-1/4", but your going to have to do something really foolish to get it to grenade on you.
Charrlie doesn't blow them up, and he uses more Nitrous than most sane people.
I didn't pull my 7-1/4 because I though it was going to fail, I wanted to be able to swap gears at the track, and LBP all in one step. (I run a Ford 8")
If your doing this for a street build, it likely isn't that necessary.

As far as the 318 is concerned, yeah, probably better do something if it's anything more than stock. If installing a rear that requires some fabrication is going to be a challenge though, you don't want to think about the V8 swap. Done a K-frame yet?

2¢

CJ

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Part of Tyrde-Browne Racing

What I got from Charlie was that he had a sure grip. I do not, so I thought it would be best to swap it out.

Am I hearing you right that you are saying, a beefed up, rebuilt slant 6 will not kill the rear so long as I don't hammer it at the track?

Also, can you expand a bit on the 318 issue? Are you saying that will be a real pain in the arse by way of a rear end upgrade, more than what I was projecting?

Eugene
I also have a 66 Cuda. I think the 318 is more trouble than its worth. A hopped up slant is plenty. The 7 1/4 is fine and you can get a SG if you look around. Most of the slants I have have either a 7 1/4 or 8 3/4. I run the 7 1/4 and if I have any problems I THEN swap to a larger rear. Other than bearing issues or howl I havent had any problems with an 7 1/4.
My 02.
Frank
Oh I use the K-H front brakes so I like to stay with the SBP rears.

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

My 70 Duster came with a 318, auto & 7 1/4. The only problem I had with the rear was a bearing let go at 65 mph on 101 near Ventura. The tire, wheel & axle walked out of the housing, smacked through the side marker, and went bouncing across the highway. Needless to say the bottom of the left side U-bolts were ground shorter and the lower shock mount was ground flat. The brake backing plate was also ground down. A new bearing went in along with the original axle & it was still running fine when the engine came out six years ago. Like everyone has said, unless you are going to a big bolt pattern the 7 1/4 will probably be fine. Just pay attention to grinding noises from the rear.