Heres what I would like...
And may work on next winter
Either cast with liberal finning or better yet, carve out of billet.
Major cost is the 17 inch x about 7 inch, x about 3.8 thick slab to start off..
So cast is really the only somewhat reasonable way to go, but will still come out at probably 700 plus, easily (likely) more...without pistons..
As far as I know NIKASIL is a proprietary coating (plated), put on to a certain thickness much like hardchrome.
I think the billet with thicker fins would be just too cool..