If everything was already the right valving, length, etc, it would be worth it. However that rear shock is of no use to you. Sell it. And if the fronts will need to be rebuilt for your weight they really are of no use either. I'd say sell that stuff and just buy banshee specific parts for you.
If you are determined to use the fronts, I believe Laegers, and Fireball use 17.5-18.5 inch shocks.