Was a special housing used for the sure-grip assembles? My car came with 2.76 open gears. The housing is noticably different then the replacement center section I have.(I'm going to use a 3.23 sure-grip...optional in 73)

Here is a picture of what's supposed to be an Oct 72 built center section.(3.55 gear) https://board.moparts.org/ubbthreads/upload2/6435961-SureGripMarkings001.jpg

Here's my original Oct 72 built center section. You can see that there is a cast pad in the center towards the top. The area under the pinion snubber has less material then the other housing. Mine has a small 9 cast into it that is facing right side up. The other housing has a large 9 on its side. There are other differences in the ribbing and the casting numbers toward the pinion.

I've got another picture of a 73 Challenger with 3.55 gears and the housing is the same as the first picture.