I would probably go the bored out b18c route myself.
As for the B20 block, and pretty much any honda sleeves, tuning makes a HUGE difference. Tuned correctly, you'll break a piston's ring lands running boost long before you hurt the cylinders. Tuned incorrectly, you'll swell the cylinder, break a piston, snap a rod and any other catastrophic failure that would make your wallet quiver.
With high HP hondas, the sum of it's parts do not necessarily indicate the total strength, because bad tuning can cause a world of hurt.
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-Harry
AIM: NDcissive
CRX and Pre '92 Civic, Engine Tech and Tuning, & Track and Autocross Forum Mod