Toyota Repair: engine difference, toyota 4runner, smog test

Question
Whats the dif in my 92 Toyota 4runner 3.0 V6 engine built in nov. of 91 than one built in may of 92?  when ordering parts im asked alot is it 4/92 or 5/92 . Thanks Tony

Answer
Even though many Toyota parts are interchangeable between years, it's important to know the year of a vehicle due to smog standards. A parts house can be held liable for selling you the incorrect part that might affect a failed smog test. In addition, many auto makers continue to improve their products and work out the mechanical bugs not to mention the errors in design. For example, Toyota had a major service campaign to replace the head gaskets on their 3.0 V-6 engine during the late 80's and the early to mid 90's due to flaws in the design. Otherwise, it's just a standard question for a parts house to ask because that's a required field in order to access the database driven parts locator program to specify the correct part you need.