the best thing you could do is slap in some higher compression pistons, and an aggressive cam.
For pistons, you could run aftermarket, or get pistons out of an older ZC engine.
The vtec head would help quite a bit. I'd probably suggest using the d16z6 head, and the d16y8 intake manifold. The y8 intake manifold flows a little better, and the older z6 head flows better as well. Then you could run either the p2p ecu or the obd2 p28. I believe the obd2 p28 was only in the 96-97 del sol si (could be wrong on that, but that's the only place I've seen them). Check out http://pub34.ezboard.com/bhondadseries
It's devoted to D series engines, and can be a great resource for parts and info.