Thanks for the kind words all! I've managed to stretch this into a 5 day weekend now, and counting. I did find some tight quench areas on the merc heads, but a couple spots at .030 and some at .035 got me to doing some grinding. Once started, I decided to take everything to .040 or a bit over as a few areas were more like 50. When I was in an area that showed .038, I blended it into an area of .042. I wanted to err on the high side of .040, not the low side. I find a dremel or die grinder is rather hard to contol so I used a worn down 4" grinding disc and traced the outline inside a standard size head gasket with a sharpie. I took out the sharpie line and a little over in the low spots for the overbore. I musta smashed a hundred foil balls today, and lifted those darn heads at least 40 times on and off. Consensus here says it will be worth the effort.
Since I hate sitting around doing nothing, I reassembled and primed my truck pan and made some main cap hard washers that fit in the milled areas on the caps. The grade 8 washers at our hardware store are too large ID. Plenty of room on front cap so I made six. Stacked them on a long 1/2" bolt and angled them against my beltsander spinning and scuffing. While much of my shop work may be a bit too'Gilligan's Island' for a lot of folks, I'm thinking these washers with their neatly beveled edge would please even the most discerning 'barners.