I have a 1988 Dodge D150 I am getting NO power to the starter.

If the starter relay was replaced (little box on the drivers side wheel well with multiple blade connections) and the starter wires are checked for bad/loose connections or maybe cut/faulty connections from that relay to the starter if still nothing save time by replacing the starter if nothing still Than its the voltage regulator/ coil or distributor get yourself familiar with a tester for future issues or use one now connect to the relay turn the key if you get numbers when the key is being turned like trying to start the truck than you got power just a bad relay or starter... my relay made noise like a klunk sound when I tried to start mine same when the starter went out it makes about the same noise just replace both and go to a parts store bring the clip that connects to the negative side of the starter and the positive side too replace both (use weather proof splice connects) that is also a common problem the connections on the starter could be to blame

Try you earth lead from the battery make sure its clean.Where it joins the engine and chassis