The front fork springs may be a little soft for you. If you really want, you could seek the advice from an outfit like Traxon see if and what it would take to get your forks correct. For me, @175lbs, the front end of my 04 is good enough as is.
The rear spring and shock are set up to handle 380 lbs. You can do wharever you want, I do not care. Here again, I'd get ahold of a suspention outfit and have them send you the proper spring. Not sure what is to be gained by buying a used shock from some other bike and trying to shoehorn it into a bike that it was never designed for. Until you get the right spring, you don't know wether your shock is inadequate or not. The shock on the 919 was designed specifically for the 919. No one that I know of has had the stock shock resprung. I don't think anyone really knows how good or bad that unit is. But we do know that it does a pretty good job when the load is matched to the spring. If you think the grass is greener on the other side of the fence and you think you can get a better ride by getting a used shock that was set up for a completely different application, off of E-Bay and having it re-done, by all means, go for it. Not me. I'd throw springs at the thing first and go from there.