I've seen kits to put a 250 on the back of a softail, but it's a LOT of work.
You have to hack off the fender strut supports, they give you a primed fender that will have to be painted. You have to go through the transmission to install the longer mainshaft that is needed. Also the longer compensator shaft/bolt.
You're biggest problem, is fitting the meat under the stock fender. If you'll notice, tire is shifted left of center under your rear fender. They almost rub as it is. Going from a 150 to a 200, I just don't think it would work without dramatic (and expensive) changes.
Wasn't aware of that Hogpro option.... but I'm not crazy about the 200 rear tire with the 06 stock belt. That thing is WAY too skinny. I can't believe that was the MoCos design. It might be fine on a Buell Blast (single cylinder starter bike), but it sure doesn't look like it could hold up to much (any?) abuse.
The fat tire only comes on three bikes. The Standard, Nightrain, and Springer. all of witch come with the five speed. I almost bought an 05 in july but I could not find one. So I ordered an 06 and was happier than **** when they came out with the 200 in aug. Lucky lady is funny little bitch.