You could save some money and gain some knowledge by making the high comp head yourself with some sand paper and time. If you look around on here you can find info on doing that. Also you can save some by making your own high flow filter with some rubber radiator hose, a few hose clamps, some wire mesh, and a bit of foam.
Another do-it-yourself performance gain you could make is drilling your carb out a bit. If you don't feel like doing that and you have the 12mm bing you can post a WTB ad on the Buy/Sell forum and pick up a used 14mm cheap.
Spend the money on the Boss pipe, some jets, and maybe a sprocket or two in different sizes.