I recently installed a 150 tire on my 2002 FLSCTI as well, but in addition to just swapping tires you should also offset the rear wheel as well to provide the clearance needed. Otherwise your tire will rub on the belt. The HD kit is way to expensive ($500) for what you get.... which is a new tire, a few spacers and a new brake caliper that has been machined to remove about 0.100" to adjust for the wheel offset. You can do the work yourself and save some $$. I spent about $160 including the machining to the caliper and the results are identical to the HD kit. The HD parts are as follows:
Spacer - 41519-00
Splash Guard - 60307-00
150 Tire - 43043-98A
Another option (had I known before) is a kit offer by a company called "Wide 1"
http://www.wide1.com/pages/725760/index.htm they offer a kit up to a 180 rear tire. Their kit includes a new wheel and fender for about $1800. They have some pics of a Heritage with their kit installed....... muy bueno!!!