Guys, I think the actual question that JAH is asking is "are the 70's parts compatible with the '89 parts?". In that case, the answer is yes, the 89 parts will work with the '70s parts, provided that they are from a '73 or later trucks.
My question is Why do you want to put the '89 brakes/spidles on the earlier control arms? If you have the complete front suspensions form either truck, there really is no gain in putting the later parts on, as they a virtually identical. The performance will be the same.
