What about using a hydraulic roller cam in an aluminum block ?

I am considering this myself. Yes, it makes an expensive engine (with the Al block that is),
but evidently you can rev a Hyd roller to 6500 or so, or even more. I think this especially true
if you use titanium intake valves, which of course adds even more cost to your already expensive engine.
But I have not heard a good argument against Ti intakes except for cost.

I think a motor like this would make a goodly amount of reliable, maintenance-free horsepower.