4x10 front speaker bracket

They made a FEW speakers with the frame built in. I don't have a pic right now but the speaker mounted with the two bolts that hold the speaker frame on the dash. That's probably the speaker frame that you would cut up. MOST A bodies from 67-76 and B bodies from 66-70 used a four hole speaker mounted to the frame above. I've been parting them out for 20 (plus) years and about 10 percent come in with the 1 piece speaker frame assembly.

Here's a good site for both stock replacement speakers and modified stereo speakers that fit in the hole:
http://www.turnswitch.com/speakers.htm