Hmm... let's see...
Replication, shadow binding, summoning, sand control, kaiten... the list goes on. Any SINGLE ONE of them would be plenty to stop the Kenshin team in their tracks.
They can't do much against 500 Narutos, regardless of the skill level difference, they're going to get hurt, big time.
Shadow binding, enough said, they're frozen, someone else slits their throat.
Summoning: A giant frog squashes them like a bug... an ant more speficifally.
Sand Control: Can't hurt what you can't hit, also, release Shukaku and squash them like ants
Kaiten: Same with Sand Control. You just can't hit Nejii, he can see everything you do and deflect it with chakra.
Sharingan: Well, with Itachi's level of skill, every single one of the Kenshin team would die inside that illusion.
Meanwhile, we'll let the Kenshin team have superhuman speed and strength. So that means they're about the level of Rock Lee or Gai.