Hmm...

A Z10 Engineering block girdle (or a modified B18C girdle)
Crower rods (or shotpeened stock rods)
P73 (Type R) pistons (for N/A)
ARP head studs

A full balancing including knife edging the crank woud be really nice. An unblalanced engine is more failure prone then balanced ones at the same RPM. A lightened and balanced system will also rev higher, safer.

That's just the block, a lot of fun stuff can be done to the head too, like:

Porting and polishing
High rate valve springs
Titanium valve sring retainers
Cams (I like Crower, as they are not too expensive and will make any grind you like with an impressive selection of specs they mass produce)
Cam gears
Valve job

..lots of stuff. You can burn through $5000 easy on a Honda engine, just don't forget: a $5000 turbo build will be faster then a $5000 N/A build.