Offshoreonly.com - Broken Nose! Magnum Maltese 270T

All,

I have a 1974 28' Maltese Magnum with new 325HP 350 Chevy Vortecs that are all Stock. 600 Holleys, Pertonix Falme Thrower 2 Distributors, and 270T Volvo Drives.
I have issues with the nose cones losing chunks of 3M Premium Marine Filler along the drive surface ahead of the nose cones. The boat was my Dad and it looks like the filler is making the drives wider. (too much)
I have Nibral 3 blade elephant ear propellers from Hale Propeller with cupped edges.

I get about 57 MPH at 5,300 RPM and I'm seriously considering ditching the nose cones and sanding those drives nice and smooth. I usually cruise at 43 MPH and 3,800 RPM out in the Long Island Sound.

Questions:
Will I potentially do better without the Nose Cones and cleaning up the filler?
What should this boat with a clean unpainted hull get for top speed but with a good cruise option. (My Dad tried Cleaver Props in the late 80s and said it did 68 MPH but without a good cruise option)