One of the (few surviving) mags did a comparison of an aftermarket Furd 9", GeeEm 12-bolt and D-60 where they both gave all the general specs (weight, etc.) and put one of each into the same car -- a Chevelle, IIRC -- and ran it on a chassis dyno to see which lost the least power. Haven't Google'd it to see if it's available online, but it's possible.

I have attempted, unsuccessfully, searched online for the one comparison I remember w/ a D-60 vs 8.75".

EDIT: Here's the first one ==> https://www.hotrod.com/articles/ccrp-0806-chevy-chevelle-rear-axle-swap/