Craig:
Yessir, I have welded them up for different reasons,...
Its very time consuming so in this case, its more cost effective to source some used heads. The only exception might be some exotic heads such as RSR or 935 ones that are worth saving.
Kirk:
Even though the MM Mahle piston domes were designed for single-plug operation as noted by the wedge-shaped domes, insufficient octane can easily cause the damage you've pictured. One really needs 93 or better gas to run at 10:1, especially in hot weather.