I went with the Nismo cam for the z24. The specs are 406/272 and after installing it and driving I can feel the power difference over the stock cam.
After break in and a little tuning, the idle was breathing much faster. After driving, throughout the rpms I noticed the powerband moved upwards of around 5k- 5 1/2k as was the stock cam was around 4k-4 1/2k. I didnt lose any bottom end and feels happy when I'm on it. Now the power doesnt cap out at 5k, thats just the sweet spot. Don't bash me but I take it up to 7k when I'm racing. I feel thats the peak output without over revving and still have enough power to pull in the next gear. BUT, just because its Nismo doesnt mean its an all out racing cam. I installed this cam in particular because it was cheap, not too big because I daily my truck everyday, and was an upgrade to stock. I figured since Nissan is the one who made the cam it must be an upgrade to stock.
My setup is a stock z24 with a nismo cam, weber 38, 4:38 rear end and everything else is stock. And run on 91 octane