depends on how bad they are bent? I am in the process of doing a complete re-build on a CB500/4 engine. I have/had some snapped fins and also some bent fins on both the head and barrel, the ones that were snapped I feathered in with a flap wheel, a dremel and hard work and the fins that were bent I used the shank of a large size screwdriver, almost the same size as the space in between the fins and tapped it through the bent fins until they were straight, no cracks no problems, once they have been vapour blasted the barrel will get a fresh lick of paint and fingers crossed once everything is buttoned up and in place you won't notice.
I did this on my Harley motor when I tore that down, same principal and no bother.