Chris, I originally looked into surface grinding until it became clear I might as well buy new ones for the price. Believe it or not, I ended up having the plates ground on a regluar rotary table, like is used to resurface heads. Just get an experienced operator and have him check the thickness of the plates at at least three or four points around the periphery as he goes to assure constant thickness and parallelness. Then hand lap with 240 wet dry sandpaper wrapped around a flat hard sanding block using a slight detergent-water mixture. Finish with 400.
The resulting surface is not nitrided so it breaks in quickly and performs well. I have run my engine for about 8 or so seasons and it is still going strong.
Jim Susko
G-Force Engineering