No one? I thought about doing the following, let me know your DIY thoughts. I can get to the lower hose pretty easily. I've done this before on another car.
Remove lower hose from radiator, let drain into pan or if you are good, have shop vac underneath, open clamp remove hose slowly and let Vac suction fluid. After all fluid drains out, place shop vac hose on lower radiator stuff with sock or rag, open up top of overflow, fill with bottled water (cheep gallon stuff) then reverse suction to radiator hose, do the same.
When all done, reconnect hose to radiator, rinse area, fill overflow tank with fresh 50/50 Dex . Burp system, start truck, run top off.