[Jac Mac]

What your really talking here is the 3.25" stroke or 3.40" stroke. If you like to rev the motor out & the sound it makes @ upper RPM then go 3.25". If you want more low down punch go with 3.40". There are lots of other mech reasons too- like rod ratio, cyl wall pressure etc.

Me, I would go with the 3.25" it 'sounds' nicer and isnt quite so 'harsh' on longer trips.---