Back in the pre-74 days, all of the OE head units had either a mono 4Wx1 output stage or a stereo 4Wx2 output stage, all into 8 Ohms..
As the aftermarket stereo biz grew then next higher powered head units having 10W per channel output having what was called a bridged output stage which was actually dual amplifier stages in a push-pull type circuit...
However the bridged output stage did not use a common chassis ground circuit, all speaker output leads (+ & -) were above ground..


Just my $0.02...

Got my radio back from Devin Duke and I went with the SM Electrotech speaker. That was where he recommended to look and it worked out awesome. It’s as clear as any new car radio, exactly what I wanted. I’ll put my fm convertor box on after the local concours show I’m in and then I should be golden. Thanks to all who replied.