After reading the link i'm not sure if the crank comes with or you have to buy that too. Besides that you are talking about a serious motor. That is a FULL blown drag motor. I don't know if its gonna be trail rideable. To keep the front end down you are gonna have to have a BIG swingarm on that beast. By the time you get that thing built, tuned, and buy the other things you are gonna need you are talking some serious coin. There is so much more to making a banshee fast and rideable than just slapping a big motor in it.
With that said I will repeat my self and say "sell your bike and buy another one that is hooked up." In the long run you will save soooooooooo much time and money. I took my bike from stock to what it now over a 9 year period and have spent a lot of money. More than i am willing to admit to. I would recommend a 421 cub, on race gas. I bet it will have more power than you can handle. In the end its your money, burn it if you want.