Anyone who wants to do this is an idiot.

 

The 4.2s used to be carbed and were really reliable. Your 4.0s are actually destroked 4.2s. They switched to EFI and smaller displacement to meet federal standards for emissions and fuel economy. I currently have an IH 258 (4.2) motor in my XJ that has been modified for EFI and is now 300cid (4.9). In short, there is nothing wrong or idiotic about wanting to do that to their motor. Its really no different than dropping a 4.3 or V8 into your rig. To each their own. So please no insults to the OP.