Hey, Steve! Wow! Sweeeet! Looks great ‘n drives great, too! Fantastic!
I’ve been workin’ on tryin’ to assist in sleuthing details, including the pre-Dave origins of the Now-Non-Crusty ‘Cuda! Without a Broadcast Sheet, original selling dealer info, or, earlier owner info, it presents a bit of a challenge, however, I’ll, in all probability, be re-connecting with formerly-frequently-in-touch MoPar pals, so, who knows? Inflow o’ some fun info may appear in the futuro!
In the meantime, re: the 8-¾” rear:
In your post #902 on p. 91, you mentioned, and, posted a pic of, the rear ring gear date (5-21-70), as well as showing the carrier (“pumpkin”) casting date, which is, as is sometimes the case (pun intended), rather indistinct. At the time, ya thought that it showed a ’71 date code, however, after playing with a photo you posted, and, running it through several filters (as well as adjusting the size), it appears that it MAY say “C 9 70,” ‘cause that final digit looks much more like an incomplete zero, than a one. Since the casting dates can be indistinct smooshes (either in whole, or, in part) I’m truly tentative about the “C” part! (That could translate to December 9, 1970.) If you can locate an axle housing date code, that may be helpful, as well, however, unless there’s date code “harmony,” they still may not agree, ‘cause of the mix ’n’ match nature of the separate pieces.
Glad to hear that the rear gear now brings some cheer!
…And, good choice on the Dana Powr-Lok, ‘cause, although the “muscle era” moniker from MoPar for their limited slip diff was “Sure-Grip,” what was, actually, inside depended upon which axle, and, of what vintage. (In ’70, it would have probably been a Borg Warner Spin Resistant.) Of the 2, many prefer the Dana.
Here’s a link to Dana/Spicer for a 15-page Service Manual/Tech PDF of the Powr-Lok. Really cool stuff!
https://media.spicerparts.com/cfs/fi...store=original
I’m, also, providing a link to MyMopar.com which presents a super-comprehensive guide to 8-¾” rear axles; their various & sundry vintages & permutations, as well as parts compatibility & interchangeability. (Note: I am not certain that this is the original source of the article, as I have seen it published on more than one site.)
http://www.mymopar.com/Mopar8_75RearEndGuide.htm
Good news, also, that the trans is staying put, gear selection wise! As Andy pointed out (Post #921), it could be harmonics. Bill @ Mostly Mustangs says “Hello!” He, also, said, “It could be harmonics, but (if the trans is good), they’d have to be serious harmonics. Usually they’d have to be bad enough that you could make a milkshake in the back seat!” …So, maybe, that trans may need a freshening or adjustment for good measure…
…However, in the meantime, ENJOY IT!