Hey, I don't have that much experience with fender amps, I've always seen them as clean amps until I read that Ross Childress of Collective Soul used fender twins for his dirty and clean sounds, I'm a huge collective soul fan. And heard that the rev used BF fenders and a pro co rat to record the solo on cheap sunglasses which is one of my favorite tones of all time. And I believe counting crows uses them too.
I recently found out there is a local boutique amp/repair man that takes any post 65' bassman and does this http://abellamprepair.com/services.htm
sounds like he marshalizes it but still....and aren't early marshall jtm45s based on the fender bassman? I wander if he could plexisize it...hmmmmm??