If you've got the 49mm forks its easy to get the slider for the other leg to make it a twin disc, much harder for a 41mm fork as then it's second hand Road King stuff. Gumtree and Ebay has both sliders new or near new sometimes for under $200 when someone else has swapped to chrome, polished or black, then sell your stuff when its done.
Your wheel might even take the second disc, just have a look. Twin disc wheels come up on gumtree or Ebay Aust, paid under $150 for mine which was new/unused and had a unused late model full floating disc on it as well (new take off) only had to buy another disc, as wheel could take twin disc's without any machining, it even had the bolts for the other disc already in it. Got the lot for less than the cost of one new disc which I would have had to buy anyway. Make sure it's not a V rod slider which will fit a 49mm, but are a different length and internals are a bit different but looks simular. USA Ebay has lots of stuff, new (Brembo with adapter bracket to fit a harley for under US$200) or near new Harley Brembo's (which don't need an adapter), sometimes the complete system is there as they wanted a chrome single disc system instead, figure that out.
Nearly all the performance bikes have twin front discs, very few have a single front disc.
Probably the cheapest way to go is a better quality caliper and as big a diameter disc as you can find, stick to quality like Brembo. Same master cylinder, hoses and sliders, only need to take the wheel off to put a bigger disc in, swap the caliper, check the spacing and bleed the brakes.
Think the Vrod twin brembo system fits as well without caliper adapters, might pay to check the bolt spacings. Might need a twin disc master cylinder as well if you put a second caliper on.
Put Progessive springs in it while its apart (search on Amazon, very cheap).
Use the SEARCH on the top of the page.
Look at the instruction sheets for progressive suspension (google search) as they give a good idea of what you have to do to swap the springs, it's basically the same procedure if you are only swapping the sliders (fork lowers).
