Just a thought, but with the FLD 112, I think you may have the C-12 for power, I think the C-15s came in the FLD 120s, longer hood.
And the dealer will only upgrade the power depending on the components of the motor involved, and a C-12 is pretty much maxed at 430 hp. You should be able to see the plate at the drivers side front of the motor, it will tell you the size and rating of the motor in HP, and torque. But as Lowboy says, there are other ways to up the power levels of the Cat as well as Cat itself. If you really think about it, pretty much anything you can do to aa Powerstroke, you can do to a big old pussy, just a little larger hahaha. Double bypass oil filters, Synthetic oil, Fass systems, propane injection, nox, water/meth etc. But you better know what your doing, because that could work out to a pretty expensive boom hahaha.
Gord.