My brother acquired a bunch of stuff from me in trade- he has 920B's, 15" Biflexes (420), 409E, 309, and 405 full range units. The 405 makes an excellent midrange too, but it's open back, you will need to enclose it.

Right now he just has the 920's up.
Pair Altec Lansing 920 8B 12" Duplex Speaker 8 Ohm 125W Tested Used Units | eBay

920's are late 80's -early 90's so are 409. 405 and 420's are early 70's.

If you don't want to go thru eBay I can forward emails.