the old b20a5 found in preludes was one of the worst motors ever built my honda. its stroke was very long and although its physically possible to bolt a b-series vtec head onto this longblock its not worth doing.

if you're looking to get more displacement ls/vtec is probably the easiest and most reliable way for you. crvtec's are very expensive and if you have the money...and someone to build it who knows what they're doing...then consider that also. also, you could find a gsr block and use that...but chances are it will be more expensive or damaged because people don't usually swap gsr blocks in favor of crv blocks.