I had the same problem with my 88 with a 2.9...one day when it got close to overheating, i realized the radiator was leaking where the plastic is "soniclly welded" to the metal part with the fins. Also, the upper hose was swollen. I replaced the thermostat with a low-temp thermostat, replaced the water pump. I removed the fan and fan clutch and added a aluminum fan and 3" spacer without a clutch. As for the radiator, mine was a thin 1-row rad. I bought a 2-row aluminum radiator that is twice as thick as the stock one. It also has twice the amount of fins per inch as stock-that helps with the cooling.