I'm wondering where to run the vent hose from the oil filler on a motor switched over to carburetors.

Is is okay to run it to the vent tube on one of the heads?

Jack

It wouldn't be a vent anymore then, would it.
Breather cans/boxes of varying quality and sophistication are available from CB Performance (low end) - to Tangerine Racing (high end).
Some people are real cheap and route the vent hose overboard, which pollutes the environment.