Some basic truths that may help your decision:
A bigger displacement engine doesn't have to work as hard to make power.
A lower-revving engine will outlast a higher-revving engine. RPM is hard on parts.
So, if you go for a larger-displacement engine that redlines at 6,500 rpm, it will outlast a smaller-displacement engine that redlines at 7,500 rpm.
You may not be considering longevity as part of the plan right now, but maybe you should be. This engine will require significant investment, and an engine that requires rebuilding in 3 yrs vs. one that requires a rebuild in 6 yrs is worthy of consideration.
I like big-inch engines that are done by 6,500 or so. I like iron blocks (yes, they weigh more. The also don't move around as much with temperature, and you'll be getting internal coolant and oil temps up pretty high in an engine like this.) Once you start moving past 7,000 rpm, stuff get's pushed pretty hard.
Just some stuff to think about...
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