Just take off the stock forks, take off all the stuff on the stem: bearings, seals and washers. Slide them onto the bombshell stem. The hardest thing about installing these forks would probably be lacing the front wheel.
Its all about preference. If you like riding high or low, stink bug or cali style (have yet to see it be done on purpose ). I like to run 4 inch with stock swingarm or +1 for freestyle and casual racing. Ive seen Tommy and Juice Hofmaster run 4" bombshells with +2" swingarm and have no problem taking on their competition in racing; no clue about racing.