really the only differenc between teh ls and crv bottoms is the 84mm bore in the crv making it a 2.0 and the pistons of course der...
But boviouslyt eh 2.0 is going to make more power, thats like comparing the b16 to a b18c.
If you are going to build the motor before you put it in (rods, pistons, etc) then I would go with teh LS bottom and just resleeve it to 84mm since that bottom is chepaer.
You can run a b20 with just pistons and rods wtih a vtec head, i have seen this run high high 11's NA before but I wouldn't advise high rpm on those oem sleeves..
Milan