[svandamme]

stick to stock.

besides, custom means you tell Wahl how to cut, he's a machinist, not an engine designer.
It's not like you can tell him , want this compression and i'm using that kind of head.
No, you have to tell him the shape of the piston, what kind of pockets, how high the dome should be..

Trust me... you do not want to go there if you don't know exactly what you are doing
And if you have to ask, you don't know what you're doing.
Get it wrong and best case your enginebuild won't run
worst case it does run till it grenades the first time you hit a certain rev at a certain temp.

Ever seen a valve shot out through the head and valve covers?? It's messy.