3.0l and 4.0l have different bolt patterns for transmission hook up, so you need 3.0l trans, no there is no "converter plate".
Computer knows what fuel mix is needed for 4.0l, so won't be able to run 3.0l, so you also need 3.0l computer, and that also means Fords passive anti-theft system will need to be addressed, you would need to get a mobile locksmith out with Ford software to add your 4.0l keys to the 3.0l computer, computer must be hooked up in vehicle to do this, and you can't drive it until it is done.
All in all rebuilding or getting a used 4.0l SOHC engine would be a better way to spend the time and money.
So IMO I would sell the 3.0l and use that money for the 4.0l rebuild or swap.
You also end up with a clean and correct VIN if you resell the truck at some point down the road, VIN has what engine came in vehicle(8th digit), yours will show 4.0l SOHC(8th digit is E) with a 3.0l(8th digit U or V) installed you could end up having to give a buyer their money back unless you made a full disclosure about the engine and had them sign off on it, AS IS doesn't cover that.
Last edited by RonD; 11-05-2015 at 08:27 PM.