There are seals for those fender-to-firewall filler plates (
these photos show a messy installation).
I think those seals usually come as parts in the inner-fender to outer-fender seal set.
Even with the seals, there are gaps. In my next installation, I'll more carefully fill the gaps with flexible black calk from the wheel-well side of the plates.
I think Denny has photos of a cleaner installation.
