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A stainless “gasket” will certainly maintain the gasket thickness and keep the top of the head where it is supposed to be but is to all intents and purposes non-compressible which is why it is necessary to use gasket cement. If the mating surfaces are perfect then a thin coat of gasket “goo” will work but how many 50 plus years old heads are in that condition? Another factor is the less than ideal alloy used in the head casting.
Again the soft head alloy might not stand it but has anyone tried using Wills rings? A gasket plate would still be needed but with enlarged holes around the bores and water circulation holes to accommodate the rings.
Alternatively an annealed copper or soft aluminium rather than stainless plate would be just a little more forgiving. It would be an advantage if as much metal not immediately adjacent to the bores and water holes was to be removed thereby increasing the load per unit area but it would still require the head to be very flat.
If a regular gasket is to be used and the degree of tightening is, as it would seem to be, an issue then would it not be possible to make a set of little gauges to test the distance between the head and the barrel? It would be an advantage to cut a series of small nicks at strategic places around the gasket to admit such gauges. By this way the head may be tightened down until each feeler is nipped. The advantage is that the compression of the gasket is independent of the torque used and head flatness should be maintained. The drawback is that when retightening is needed due to settlement then another set of thinner feelers would be needed for each re-tightening. On the positive side such a set would only need to be made once. What thickness should such feelers be? I don’t know, I would need a well-used gasket to measure for a final size, also a once compressed one for a starting point and I have neither to hand.
It should be noted that annealed copper does not stay very soft for ever, if a copper gasket is to be used it should be annealed and used. Avoid flexing, it will work harden it even if only a little. Copper will also age harden although it is a fairly slow process. After annealing vinegar, Citric acid or a fizzy cola soft drink will clean the copper quite effectively.
Aluminium sheet may be rendered soft by the use of soft soap as a temperature marker, (other types of soap might not work as well due to additives), when the soap goes brown the right temperature has been attained and the aluminium should be quenched. Clearly this is a somewhat agricultural method and there are so many grades of aluminium but at least it gives you an even chance. Some grades of aluminium also age harden, indeed some used in the aircraft industry will age in an hour so early fitting is recommended to be safe if you are unsure of the grade.