I just bought a 2 yr old house and the toilet whistled everytime it was
flushed. Bought me a Fluidmaster Whisper Fill Valve and Flapper.
Installed the new fill valve but the flapper was not needed because
this toilet bowl had a round plastic overflow pipe and the "round
plastic flapper substitute" lifts up, the tank drains, then it settles
down on a large red washer (about 3 or 4 inches in dia.) to stop any
more water going into the toilet. The top of this fill pipe has a screw
in cap that has a place to insert the refill tube. A short way down the
pipe is a brackt sticking out from the pipe where the tank lever arm
stick thru.

I have never seen this type overflow pipe before - hope I don't again -
it leaks so very slowly in the washer area and then after enough water
has leaked, the fill valve activates again. Think I finally got it to
seat good enough that it doesn't appear to leak anymore.

What the heck is the name of this overflow pipe?

Can it be replaced (easly) with a standard fill pipe a standard flapper
valve seat?

Thanks in advance.