I'm getting antifreeze in my #8 cyl. in my 4.6 tritron v-8 f-150.?

Mechanic says could be cracked head and or head gasket. Can heads be re-worked or is the piston scuffed ? Do I need a new engine ? Also was running 10% ethanol off and on since 2007. Truck is a 1997 with about 80,000 miles