wow 270k? my 90 only has like 209, lol. but anyways, sounds good. just dont get drilled rotors i always hear they crack after awhile. is the clutch still good? you could get like a stage 1 ACT. but onto the suspension, if you have the money, get the Tein basic damper (around 800-ish if i remember correctly)
http://www.inlinefour.com/teintypbasda.html .
well since the high miles i would suggest a new motor (or just another one with lower miles) but you said you dont want to swap the motor. do you want to go turbo or all motor or nitrous or what? first things first, get an intake, a good header, and a nice free flowing exhaust. as for internals, if your goin for all motor you could get some aftermarket high c/r pistons then pick up some ARP fasteners for the rods and head studs etc...then a nice stage 1 maybe stage 2 cam (you'll need aftermarket vavle springs and retainers for stage 2...could get away without them with the stage 1 but if you have the money, it wouldnt be a bad idea) i dont know how good crower cams are for D series but:
http://www.crower.com/cgi-bin/detail.cgi?prod_id=63442z
check out
http://www.superhonda.com/forum/forumdisplay.php?f=87 im sure you will find tons of info there