Hey Peter, congrats on the new bike! Although there are several manufacturers that make whitewall tires, Avon, Metzler, ect. As Dennis said, the only companies that make a whitewall in the size(s) that will fit our bikes is Maxxis and Dunlop,if you can find some leftovers. Good luck on finding Dunlops though..... Dunlop quit making them. You might be able to find a rear but I searched nationwide to find a front with no luck. I even called Dunlop to see if they would be able to track them down....nada. So that leaves us with Maxxis. I bought them and have been very pleased with them. They may not be quite the tire compared to Avons or Metz's that everyone raves about but they are leaps and bounds beyond the stock 'Stones.
I bought mine online through a company in Dayton, Ohio called
Tires Unlimited . Called them up to check stock, they had them, and they showed up at my door two days later. They had a great price on them and I bought tubes as well, I believe they even through in the rim strips.... oh wait, mag wheels.... you won't need them. Anyway, I would buy from them again for sure.
I can't speak for sure about the Speedy fender and bracket arrangement but on an America some mods have to be made to the fender brace, cutting it out in the middle or raising it up slightly to clear the slightly larger 120 tire.