the b20b blocks have 8.8:1 cr, but the b20z, and some of the b20b jdm blocks have 9.6:1 (not all of the jdm ones do so don't think just cause its jdm its the better one)

using a b20z block with a vtec head will work, but the valve reliefs on the piston aren't large enough for the vtec valves, therefore will cause clearance issues if you even slightly advance or retard the timing. your best bet is to put aftermarket pistons in the b20 block, but that means you have to tear it down, so you might as well do rods too. but if you are going through all that expense, why not just sleeve an ls block to 84mm and go from there, it'll be cheaper in the end