New Kelsey Hayes 10 x 1.75 brake drums with BBP??

I just had a fella from another site PM me that these drums are for 66-70 B-body with /6 and 7.25" axle and have been discontinued for decades, unable to confirm though.

That has some correct information.
Yes there were /6 equipped B-bodies that used BBP rear drums with 1x1.75" shoes.
Drum p/n 2534 173

Shoe & lining package for all 4 brakes was unique because of the combination.
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Rear wheel shoe & lining package was the same as A-bodies
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(1967 Parts Book)

Whether those finned KH are for Chrysler or another manufacturer, I don't know.
KH made OEM and aftermarket parts for all of the manufacturers. For example Ford also had a 10 x 1.75" rear drum. Shoes are virtually the same, but aspects of the drum are most likely different.

Here's an example of the SBP version - aftermarket, IIRC Wagner.
Sorry I don't have an inside view
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There was also a version with wider flange or lip that sometimes shows up for sale. Pictures here: "Bell" style drums

Here's Centric's dimension's for the SBP version. For the BBP should be the 4.5" bolt pattern and probably 1/2" holes for wheel studs.

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