If you go with a 3.00" main 4.21" crank, .010" over 455 pistons (same bore as a 400 with .040" over bore), SD ported KRE 290 cfm heads, the CR will not be too high. You could even take that 400 .060" over and get more cubes. If you go this route with standard '68 iron heads, then yes the CR would be too high. You can do it with 6X heads but you won't get the peformance of the KRE heads.
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469 (455 + .060") with the Edelbrock RAIV cam, Ported 6X-8 heads with 1.77" exhaust valves, 100 cc's, "0" decked block for 9.3:1 static CR, Eagle 1.65:1 roller rockers, Edelbrock RPM manifold and Edelbrock 750 carb., 1.75" x 3.0" Hedman Headers, 2.5" flowmaster exhaust system with "H" pipe and Dynamax super turbo mufflers. 200-4R with a Continental converter, 3.07:1 12 Bolt Saf-T-Trac
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