I think it depends on which heads are on the L26, for power estimates.  The stroke is longer, bore the same, but, apparently, the L26 was developed as an emissions engine, in the beginning.  Usually there's "no replacement for displacement", so, with the same parts the L26 should make more power.

Choices are really about the goal.  Lots of possibilities.

Sounds like by ditching the flat tops and using the roundtops the power should be a little better?  Flat top was the emissions carb? . . . What are the head options? After market head? Different valves? Do you like the petronix ignition and what sort of a setup? Thanks. . . 

Too many possibilities.  I'd get one running first and see how you like what's there.  There's a ton on the internet about heads and cams and carbs and stuff.