Putting two speakers in the dash, when it was only built for one
Your 66 should have a 6x9 speaker mounted to a plate with two ears that hold it to the dash. Going to two speakers in the stock front location actually works quite well and sounds better than you might think. Contact '74 sport for some brackets to do the job (see this link for some photos http://www.forabodiesonly.com/mopar/showthread.php?t=25433 ) or make an outline of your 6x9 speaker. Cut an aluminum plate the same as your outline and cut openings for your new, small speakers and then mount those to the aluminum plate. Then mount the plate to the original bracket. Cover the top with some new speaker cloth and mount it up. Put some blocking capacitors in-line to eliminate some bass so those small speakers don't over exert themselves trying to create deep bass. (A sub in some stealth location elsewhere in the car can cover those deep bass duties better anyway, or in the case of your car which has rear speaker locations, the rears can contribute the bass...) I put the twin small speakers up front on my cars and believe it works quite well.
Your 66 should have a 6x9 speaker mounted to a plate with two ears that hold it to the dash. Going to two speakers in the stock front location actually works quite well and sounds better than you might think. Contact '74 sport for some brackets to do the job (see this link for some photos http://www.forabodiesonly.com/mopar/showthread.php?t=25433 ) or make an outline of your 6x9 speaker. Cut an aluminum plate the same as your outline and cut openings for your new, small speakers and then mount those to the aluminum plate. Then mount the plate to the original bracket. Cover the top with some new speaker cloth and mount it up. Put some blocking capacitors in-line to eliminate some bass so those small speakers don't over exert themselves trying to create deep bass. (A sub in some stealth location elsewhere in the car can cover those deep bass duties better anyway, or in the case of your car which has rear speaker locations, the rears can contribute the bass...) I put the twin small speakers up front on my cars and believe it works quite well.