any benefit to swapping heads?

yellow
it's not the valve size it's the velocity
Think about putting your valve seat where the top cut is on your 45 degree valve job
the old 45 degree seat is most likely well sunk on old heads and impossible to put a good valve job on- well putting larger valves in is one way
sunk seats suck big time
if your cam profile is based on flow demand you do not have to kill low lift flow to prevent reversion
open the intake later