I just replaced the exhaust on my Chevelle and have two Dynomax super turbo mufflers for sale.  They measure 4.25" x 9.75" x 14" with overall length of 18.5".   Steel construction with aluminized finsih.  2.5" inlet/outlet.  Not bad shape, guessing abut 10,000 miles on them.  Summit part #17784.  Don't know what they are worth, $15 each?

Ive never seen those brackets on Chevelle mufflers for hangers like that. Is that a 69 thing?

Nope, I think it is a Ford thing. I looked at the summit catalog and they are for a Ford. Don't ask me how thing got on my Chevelle.

Why are you changing ?

A couple of years a go when I put tips on the exhaust, the guy that did it for me said the exhaust was a mess and soemday I should update and do it right. Well it was time to do it right so with the new exhaust I put on new mufflers.