As you've already learned, you have a 4.2, not the 4.0. Also, as you've found out, that is an aftermarket valve cover. As for the carb, the connections don't match the Motorcraft 2150 I have in my '87, so I'm going to guess you have the Weber 36/38.
Tuning the carb is not that tough of a job. Do some Youtube searching and you'll find some great videos on how to make the adjustments.
1996 White ZJ
1987 Maroon YJ (sideways build)
1996 Forest Green XJ
The "sideways" build thread:
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