[jamesm]

There is are big differences between the '74 model and the '75-'76 models. The '74 model used a normal exhaust system (very similar to earlier exhausts), whereas the '75-'77 models used thermal reactors. These reactors make underhood temps soar, and cause a lot of the heat-related problems. Also, the '75 and '76 models used a 5-blade cooling fan in place of the 11-blade fan used earlier. The fact that the '77 and later engines went back to the 11-blade unit should tell you something. In general, a '74 2.7 will be much more reliable than a later engine. Later engines that have been rebuilt AND converted to earlier specs can also be very reliable. However, you can't ditch the thermal reactor in most states because of smog laws, so that problem remains. For a 914/6 conversion this won't be an issue as the thermal reactors can't be used with the required 914/6 exhaust systems, anyway. For a smog state, this makes using a post '74 engine illegal.