Pistons will swap over, unless your decked you'll need to swap over the H23A1 crankshaft to use the H23A1 rods. H23/H22 block castings are indentical, differences are all internal and most parts are interchangable with the exception of intake/exhaust manifolds (upper portion of H23A1 intake manifold is the same as H22A/1/4), obviously head internals are not interchangable as the H22 has a VTEC lobe where H23A1 does not, valves should be the same dia though. Distributors are interchangable along with all of the sensors. Cam gears are different, although H23A1 cam gears have the same teeth as B-series. Timing componets are different (teeth wise), H22A/1/4 uses a hydo tensioner for the timing belt where H23A1 uses manual (you can swap hydro for manual and vise-versa), crankshaft pulley is the same, flywheel/clutch are the same, axles/inter. shaft the same, accessories like a/c, p/s, etc are interchangable. If you have any other questions feel free to ask.

-Mike