Welcome to NICO!the 280Z was made from 75-78, it was the tail end of the s30 chassis which also included the 70-73 240Z, 74 260Z, the 280Z had 2.8 inline 6 (hence the 280Z designation), equipped with bosch L-Jetronic EFI, they came in 4 speed manual or automatic, and in 77 and 78 they also offered the overdrive 5 speed manual, also 77-78 got slightly improved rear brakes, and optional factor air, the earlier cars had smaller bumpers and weighed a bit less and the 75 had the non egr intake with the N42 cylinder head which would offer the best performance
performance aprts are available from your nissan dealer in the form of Nissan Motorsports carts, you'll have to get a catalog or find a dealer familar with the motorsports division, zcarparts.com offers replacment parts performance parts and some used parts, and they have great customer service, also check
http://www.blackdragonauto.com/ for other replacement parts
when looking at a car rust is the number one issue, buy the best chassis you can find, the other parts are a lot less difficult to come by
stock numbers are in the neighborhood of 150hp, I've seen N/A's run will over 200 hp at the rear wheels! stroker setups have been known to reach the 300 range, and if you go turbo like myself, 400whp can be easily achieved
have a look around and be sure to look in out classic z section as well