Here are some of my favorite links for working on my Datsun 240z. These websites and forums all have a wealth of knowledge to draw from.
Forums
Websites
Datsun Z Garage (engine building and modification tips)
Part SupplieRs
ZCarGarage (Datsun parts and services)
Classic Datsun (Datsun racing and period correct parts)
Z Car Source (Datsun part suppliers)
Z Specialties (Datsun part suppliers)
Motorsport Auto (The Z Store - Z Car specialty store)
Arizona Z Car (Datsun Z upgrade parts)
Zeddsaver (Datsun Z part suppliers)
JDM Car Parts (Datsun part suppliers)
Techno Toy Tuning (Suspension upgrade parts)
Rebello (Engine Builder)
Datsun Spirit (Engine Builder)
Datsun Zstory (Headers and Exhaust)