I welded on my new stealth when I first got them, reshaped the combustion chamber some and added some meat around where the head gasket area is. I did not get them heat treated and have had no problems with a 12:1 470. I used 5356 filler metal using TIG. It's been about 3 years and about 300 passes down the track. The only problem I had was one of the heads cracked on me last year around one of the outer head bolts and into the water jacket. When I pulled the head, there was no grove where the head gasket "ring" rides on the so called "softer" area. I gouged/welded upthe crack, had the head shaved to remove warping from welding and have had no problems.