Aloha,
I agree with Craig. Each have their virtues and some faults, but aim to please and stay in business. Get a catalog from the major parts supply houses. Each have a few unique items and many of the same items. One may have something in stock when the others are out. In any case the newer catalogs or filled with many exploded views of systems and are mini reference books. Also get a Haynes or Bentley workshop manual. These are now available on CD, but I prefer the paper version. The internet is a wonderful resource for gather parts, information and specialist in repair things on your car. An important thing to remember is that your TR3 was made of pieces that are repairable, not like most modern cars were replacement is the only option. Good luck and use this forum for support and encouragement.