I have a 1970 #3177, which I am replacing the entire drivetrain and suspension. No mods to the exterior or interior other than the steering wheel, the shifter knob and the climate controls.
Engine: I read an earlier quote by someone here who said, paraphrasing: "I want the old style with the new technology". In my case, I want the old style with the old technology, squeezing as much out of it I can. Therefor, I have shipped my L24 numbers matching engine to Rebello Racing for their "Purist" engine build. Lower block is over-bored and stroked to make my 2.4L into a 2.84L. Head is bored for 280 valves, port&polish, new custom grind cam. It will be dyno tuned. All in all it will make around 270 HP, up from the 151 stock HP. This is plenty of power for a 240, in my book. I don't want Fuel Injection or Turbo; my SUs are awesome! I really don't need or want more, even though I plan on racing with TrackDaze. I will be trying my best to not lay rubber when the light turns green and get that ticket (it is my DD as well).
Transmission: 1982 280ZX close ratio 5-speed transmission, completely rebuilt.
Differential: Very rare R200, short-nose, 3.9 ratio, Gleason/Torsen racing ATB (T-2R with preload clutch packs: http://www.torsen.com/products/T-2R.htm) LSD diff. One of 80 ever made for the R200. I think it is a 5:1 torque bias ratio, but I am not sure about that. The link says "With a high torque bias ratio, the TORSEN T-2R can deliver up to 85% of available torque to the wheel with traction." I think that a 5:1 ratio means 5/6 of the torque goes to the tractive wheel, which is .833, damn close to the 85% mentioned in the link.
Suspension: Tokico 280 HP springs/Tokico Illuminas/Suspension Techniques front anti-roll bar/full urethane bushings, except the T/C rods. Thanks JohnC!
Rear disk brakes: from a 240SX, for my 14" wheels.
Anyway, I thought I would just throw out my "favorite" modification preferences as an alternative to consider.