hi, i am looking for some info.my 1989 commanche has an issue with the rad.all the cooling fins have turned green and are falling off.this is not too much of an issue when just tooling around in the fields,but put it to any kind of work and it starts to heat up pretty good.So my question is what would be compatible for and exchange,these trucks are hard to find and the ones with a 4 litre 6 are even harder.i look forward to ant input from all the experts out thee

mike