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Southcross, speaking of raising compression ratio;
Since you have some building experience, tuning and race experience, I suggest talking with guys (there are several) who race that Rabbit engine you have. Rather than just thinning the head gasket and hoping for the best, there might be a combustion chamber modification that will break up charge statification and improve burn (after all, that is an older engine you are working with). Some head porters call this modification "fast burn" chambers. At the same time, having the same guy touch up the bowl area under each valve, and of course matching the intake ports to the intake manifold, 60-80 grit cartrige roll to roughen up the port to improve laminar flow to improve intra-port fuel atomization may of may not help. The idea with fast burn chambers is to better mix the charge through promoting swirl in the chamber just before combustion, to reduce detonation and promoting a more complete burn. If you can do that, you can raise the compression ratio and use the same octane fuel. The engine becomes more efficient through better cylinder filling. That's the theory anyway... much more difficult to get it all correct and get it to be an improvement without a bunch of trial and error.
Oh, I suggest you take an hour or so and check out and read about "singh grooves in cylinder head" by doing a google search. This DIY mod seems to help out older engines and enable relatively more CR with the same octane fuel. I don't know anyone personally who has tried it, but it sounds plausable and quite a few DIYers have blogged about their personal results.
I hope this helps
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