Also needing help to identify a 50's rear end

[mo381]

I think this is a 49-53 olds rear end, but I am not sure.
It is in a 51 Super 88
I am pretty sure it has 3.73 gears

Looking at the front of the drop out it has the following numbers.
left side middle cast 513261
lower left side 8 stamped on the cast square
and E 17 1 cast on the lower right side.
Also11 cast on the upper right side.

I am concerned because of the 500+ hp and built tranny and that this could be the weak link.

Thanks for any help you can give.