Technical What rear is this?

What rear do I have here?
The guy I got it from said he got it with a project car he bought, but didn't have any info on it. He didn't even realize it was narrowed. I only paid $20 bucks for it so if it's junk, I didn't gamble much away.
The numbers/letters aren't very clear. I think it reads GM 8707806. But the 8's could be 3's too. Not sure. Not pictured is the centered drain plug.
Even if I don't use it for anything, i'd still like to know what years/vehicles this is from.

 

Looks like a 55-64 Chevy car unit.

 

Kinda looks like a ford, so i'll guess tri five Chevy.....?

 

That sure looks like the 55-64 GM rear. 8.2 inch ring gear. Not the strongest, but will hold up behind a good small block, but no slicks or sidestepping the clutch.

 

55-57, the experts will identify which year by the shape of the housing ends

if the date code is visible on the center section, you might be able to tell the year from that. And something about a drain plug one year only?

 

Thanks guys. You nailed it. Using the info all of you gave me, I did a thorough web search and came up with this. The 1958-64 housings were in cars with coil springs, so that rules them out. That leaves tri-five. The casting number (its 3707306) on the 3'rd member is 1955-56, but the axles / bearings and housing looks to be 1957. It has a center drain hole. That was a 1957 year only thing. Also i found that 55/56 bearing retainers are farther away from the axle flange than 57's. It pictured both and mine looks like '57. So I guess that it. It's a 1955/56 3'rd member in a 1957 housing with 57 axles/bearings/retainers.
If I do use it, it will be behind a mild small block or flathead v-8 in a model A pickup.
I'd like to use a buggy spring on it but I think it's too narrow. What if i flatten the rear cross member and use a shorter lower modern leaf spring. Anyone have any suggestions on that issue?

 

Good to see that someone knows how to search, when they know what to search for

I don't have a spring answer, sorry.

 

I narrowed my rear and a regular model a transverse leaf spring was way too wide and so were others. Below are a couple pics of what I have. Going in a 30 coupe.

I designed it to be adjustable ride height. I don't wanna steal your thread. If you have any questions just lmk. I have a build thread that gives more details.



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How wide is it between backing plates?

 

It's right around 49". I also measured the spring perches on an "A" rear, and it's close. It might actually work with an A or T spring.

 

That should do it I think. I'm putting A perches on a 57 ford rear, got a SoCal hanger, puts spring behind instead of on top of axle to get her down a bit lower....I think I read 48" is the measurement...