Hey now :-), from a functional standpoint, there's nothing wrong with wanting to improve the brakes. They, like everything else on the Speedmaster / America are of good quality and performance, but there's never anything that couldn't be improved upon :-) That being said, there's not too much out there for what you're asking about Chuck, BellaCorse sells a Norman Hyde upgrade that is centered around a new caliper, but that doesn't do us any good. Brent @ newspeedmaster.com, probably sells the most comprehensive "upgrade" available, which is an EBC full-floating rotor conversion, along with EBC HH compound brakes. Other than these, you can experiment with using S.S. braided Lines, and different compounds from different brake pad companies, and BellaCorse sells a span-adjustable brake lever that we can use as well. For myself, more as a curiosity than anything else, I snagged a pair of Triumph TT600 brake calipers (opposed 4-Piston) off of Ebay for a relative song, and will eventually get around to see about adaptation. The biggest problem right now seems to be that the fork mounting points are about 1/2 a centimeter too far apart on the TT600 calipers; otherwise can't see what would prevent them from fitting on the Speedmaster. If and when I can physically mount them, the next headache would be to experiment (without killing myself in gory fashion) with the calipers to ascertain their functionality with the Speedmaster reservoir / master cylinder. But that's another story for later I guess.
