F = E with longer MR blades from 520N and extended tailboom with adapter - C30 Max TO 375 hp
FF = as above with MGB from 600N as retrofit. C30 Max TO 425 hp 0-50 kts.
Incidentally the 600N MGB can be fitted as a retro to D, E, and 520N for more durability and higher TBO. It is a much better gearbox.