why an h23? if you are going to go h-series (which i don't recommend) you might as well go h22a.
you need an h-series mount kit
other than that, it 'fits' but you will need to move almost everything from your firewall along the intake manifold, bang out your fender for crank pulley clearance, and most strut bars wont fit over it.
after that, you have extra weight up front = poorer handeling. after that, you will break axels monthly do to the poor angel that they are forced to sit at in a civic.
It all can be counter acted, but you are better off with a b-series.
only way i would go h-series would be if i were to build a drag-only car