There was a universal one that JC Whitney sold at one point. I found similar for sale on Ebay or at Vintage Car Audio....
http://cgi.ebay.com/ebaymotors/Custom-Autosound-Univers...165791QQcmdZViewItem
http://www.vintagecarradio.com/store/product_info.php?products_id=21
This should bring the music closer to the ear, (which is what I was considering at one point) and is a fully reversible solution. Door speakers are pretty useless in the Pantera and then the holes in the panels are permanent.
Good luck,
Julian
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