The original MGR horns have proper connectors on them like this. OEM for the twin horns is Hella, although when changed to a single horn then they seem to be FIAMM but use the same connector. Spade terminal sounds like aftermarket horns have been fitted in the past.
2004 is around the PPD changeover as my ZT only had the single horn being a 04 build, but I added the second horn with the correct loom and they were the Hella with the correct brackets.