Not knowing the frame , Softail , Dyna , Touring etc. for battery size , I'm partial to the H-D batteries because the terminals have different attachment locations and are the AGM style . I would go with nothing less than a 1.4 kw starter , preferably a 1.7 kw from Spyke or Volt Tech . I would also upgrade the battery cables to something like the Terry Components Flexy cables . Another thing I suggest is to get rid of the stock ring and pinion gears in favor of the 9/84 or 9/66 gear set that'll give your new starter more oomph and stronger gear teeth . Kinda like taller gears in the rear axle of a hot rod . I would also install a stiffer clutch diaphram spring to keep the clutch plates clamped together under the extra torque generated by the 113" !
Disclaimer : Don't believe anything I say unless you are absolutely sure that I know what I'm talking about .