aftermarket parts

I have a 2003 Ford Explorer Eddie Bauer edition. When I go to buy aftermarket parts (ie, Autozone, etc), sometimes the parts are not right when I get them, just listing the vehicle as a v8 Explorer, 4.6 Liter. Does anyone have any idea what engine system would match so I don't keep getting...

I would like to start off this area with two names of aftermarket companies that I think make parts better than OEM. For suspension = MOOG Amazing stuff, lasts longer than OEM And Felpro Their gaskets are even better than OEM These are two companies I have never gotten anything bad or defective...