Need a plan - component selection for restoring 68 340 that runs on 91 oct

get some Sunoco 260 or Cheveron Custom Supreme and you can run as close to the 1968 4 speed as possible
I'm assuming he wants it to look as stock as possible

good idea AJ
just using a thicker head gasket means that you have to give it more throttle to get the same amount of go which just creates more heat and not more power
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But, it all comes back to application.
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Exactly
If standard crank is a must I'd pick the design of one of the KB quench dome pistons and get bids from the custom piston mfgs
I first used Arias but since then have used most of the majors (mostly for BBM but SBM should be similar)
been doing this since they dropped compression in the early 70's and the good gas went away
there is NO good/ cheap solution pick one
tried them all welded up the chambers, big mill jobs plenty of Dyno time on the Big Blocks but same problem
stock cam i optimized for high compression (and long warranty life (no lifter noise) with long ramps) would not think of using it today
and for low compression it leaves a lot of torque on the table (you have to use low gears and buzz it up to make it work and even then there are better choices)