Since it's a B-block, it'll take a B-head. It won't take the cylinder head from the D-series... from your post, sounds like you're referring to the D17.
Since B-heads will fit, that means the 160 hp B16A head or the 185 hp B18 head can go on the block.
Which means around two hundred horses (maybe about 180 to the wheels), give or take, depending on whether your bottom end will hold together and how good your tuning is.
conversion guide here:
B20/VTEC Build up Guide - Honda, Acura Tech Website, tutorials, tuning and HOW-TO's. Drag racing, street racing, road racing - C-speedR.com
As for economy... errh... fuhgeddaboutit.