The easy way is to get larger wheels and tires. The stock tires were "about" 25.4 inches in diameter. If you get a wheel/tire combo that is 10% larger than that, your effective gearing is 10% taller.
The hard way can get really really expensive.... 2nd gear is a part of the main-shaft in these transmissions, so you have to replace it with the "904 mainshaft", which is a very pricey part. If you don't want to pop for that, then you're pretty much stuck with the stock 1st and 2nd gears. Other gearsets can be swapped around, and you can even "flip" them so the drive gear is the driven gear and the ratio is inverted.
A list of the different gear ratios that have been made for the 901-based transmissions (like ours) can be found at:
http://members.rennlist.com/chuxter/901&915ratios.htm
Many of those ratios are now quite hard to find. Paul Guard at Guard Transmission (
http://www.guardtransmission.com/ ) can supply you with most of them, but the cost for many of them is pretty steep.
--DD