Yep, these wires sound like the old WR-5904. Most likely original, and well overdue for replacement. Unfortunately, they don't make the Explorer-specific set anymore, and the replacement, WR-6034 fits several vehicles of similar vintage. I just installed those, and they seem to be much better quality, with silicone insulation. On the flip side, they come as a loose set, and you have to transfer all the separators - assuming that those can be salvaged. No numbers on them, so it's a bit of a matching game. I found #7
to be too long by 3-4 inches. Also, the double locking tab on the coil end seems to be a mixed blessing, and very hard to latch properly.
I don't know about best plugs, but they should be double-platinum, whatever the Motorcraft part number assigned to those. I believe that Autolite has an equivalent. Get ready to receive a bunch of opinions on this subject, as for some reason, plug choice seems to be a highly emotional topic with some members here.