My buddy has a 58 Savoy and wants to put a newer style 8 3/4 rear in it. Which 8 3/4 will fit without too much modification?

E- body fits perfectly except the perches will have the pinion too high, cut and reweld perches and your there

The C and E body both share the '58 spring pad width, overall width varies but both are wider than the '58.

FWIW I have 15X8-4.5bs w/275/60/15's dead center in the wheelwells of my 58 Suburban

Do you think a 69 b body would be perfect because its not as wide as the e body????? Do you know what backing platte to backing plate width is????

I'm not sure this will help you, but I'm installing an 8 3/4" 1968 Roadrunner rear housing in my 1948 Plymouth. I measured approximately
55 3/16" from the flange outer mounting surface to flange outer mounting surface, with no brake backing plates in place yet. Spring perch placement for my vehicle required 46 1/2" center to center distance. I believe that the 1969 B-body used the same rear housing. Hope this helps you out.
Additionally, I was informed by the machine shop assembling the rear, that the center section (not from a Roadrunner) had some serious wear issues (741 case, open type). Needed new cross shafts, spider gears, side gears. Seems that those parts are no longer available, so I was kinda forced to replace the internals with a True Trac Posi unit. Spent nearly $1000 total for the housing, center section, carrier bearings, Green axle bearings, seals, labor, and all new brake parts, bead blasting old drums and having them turned, etc. I might have been better off finding an alternative, but had too much invested to change directions at that point. Just be forewarned that your investment in the 8 3/4" unit might be considerable.

The Standard Catalog of Chrysler 1924-1990 list the front wheel tread of all models as 60-29/32 and the rear tread for all models as 59-39/64. One would presume that to mean the width of the wheel mounting surface.

My old Direct Connection book lists the standard track width by body style. 8-3/4
A body, 67-72 as 55.56 Spring seat center to center 43.2
B body 62-70 as 59.2 spring seat c-c 44.0
E body 70-74 as 60.7 spring seat c-c 46.0
B body 71-74 as 62.0 spring seat c-c 47.3
B body S.W. 71-74 63.4 spring seat c-c 47.3
Also lists 9-1/4
B body at 62.0 spring seat c-c 47.3
and a B & C body at 63.4 spring seat c-c 47.3
and an F body 8-1/4 as 58.50 spring seat c-c 44.46
Have fun. Gene

Many thanks to everyone that replied
Alot of good information here.....
My buddy (Lil-hemi) has somethin to work with.

Just a couple of those for what it's worth things.

If your friend is wanting to upgrade primarly becasue of the brakes and tapered axels AAJ makes a rear disc brake conversion for these axels that may be an alternative to swapping the whole rear end.

I ended up with a couple of 9 1/4" rears out of 77-8 full size Chryslers some years ago both with 3.21 Sure grips. I paid less than $100 each for them because nobody else wanted them. They are 1 1/2" wider than the stock rear ends on the 57-8 Dodge and Plymouths (3/4" per side). The spring perches had to be relocated but that is pretty minor. One ended up under a 57 Coronet I had and the other is under my 57 Plymouth.

As it happened I built 76 Dodge D100 a couple of years ago and in the process discovered the mid 70s dodge pickups used the exact same axel with the exception that the truck spring perches are located on top of the axel (which would need to be changed anyway). I bring this up as the pickup 9 1/4 are also more likely to have a bit deeper gear set (3.50) and possibly a SG. Thought I'd throw that out as an alternative in case your buddy is interested.

Thanks for that info Mike.....