Aussie Speed head gasket.

Yup Charlie knows his slants.
The machine shop that has the head I'm gonna use on mine called this morning, finally had a CC number for me, mine is at 60cc. He had looked it up somewhere (seems like machine shop people have access to stuff that those that aren't in that industry, don't.) Said that was also what his lookup said it should be. Been waiting for that call to determine how much is want shaved from mine. I was wanting somewhere between 46-48 cc for my build, knowing the figure I've seen to shave per CC of chamber volume to lose is something like 0.0066" so knowing I had 12 cc to lose I did a quick calc in my head (hey I was driving at the time) and told him to go with 70-thou. Later I figured it out, 12 thou CC volume loss x 0.066 came back at like 0.78" to shave. But add that to the 0.030 off the block already comes to .100 total between block and head. With the 0.060 Aussie head gasket vs the original 0.020 steel shim, I can add 40 thou back, leaves a net added squeeze from stock to only 60 thou. Once I get it back and can lay one of these other head gaskets I have on there, which are more realistic 40-thou thick, if I can use it,(because of that fire ring issue) might be borderline too much for a daily driver on 87. With the Aussie gasket, at 70 thou off the head and 0.030 off the deck,I'd have to go back and look but as I remember that gets me to 8.7-8.8.
I'll have to figure out what it would have been stock, with the steel sh gasket and uncut block and head, will be dreadful. Probably what.... 7.5 if I'm lucky? Though the engine was apart when I got it, no pistons or rods to be had. So I couldn't measure the original in the hole number at TDC. I have a hard time believing that this engine would have had the pistons .210 in the hole as built on the assembly line? I have heard that silvolite adjust the compression height on o/s pistons to "make sure" that a new engine built with their pistons won't be any higher compression than stock original.
My question then becomes where did all these publishers get their numbers from when they listed engine specs in the manuals of the day?