Are Delphi and ad delco not the same thing?
Maybe, maybe not. AC Delco is GM's brand made by approved vendors for parts. Delphi is a company that may have made those parts originally as a part of GM, or after. If Delphi makes it, they likely made the original. A current AC Delco part could be made by anyone GM choses. Delphi closed a lot of plants when they went bankrupt, so some stuff now comes from China or Mexico. When I bought my Delphi radiator on Amazon, it was basically a dealer part, made in the US, but sold at a low price through Amazon. The plant that made it, in NY, went back to GM, as part of the bankrupcy restructuring, I believe.
So in short, I typically by Delphi or AC Delco, but with the understanding that it's possibly that neither are exactly like what my truck was originally built with. I beleive both to be high quality in most cases. I did pass on the new made in China Delphi heater fan/blower, However. I bought a Canadian made one off of Amazon...... can't recall the brand, Though.