I think the 5.0 would be more of a challenge than the 4.6. It's one thing to just swap the engine and ECU from the same generation, but you might run into all kinds of issues with the 5.0. Things such as how to drive the tach, speedo, dash lights - all the indication stuff - that runs through the ECU or other module that was originally on the same generation as the 5.0. Also, you have to worry about hooking up the electronic controls to the transmission and any speed sensors, etc and hope that the signals are the same between the generations both in terms of type (frequency, voltage, current, etc.) of signal as well as the range. After that, you have to figure out how to hook up cooling lines, tranny lines, the accessories, etc.
Since your Explorer was available with a 4.6, you should be able to swap in the same engine and transmission and all the electronics. It's not just a matter of emissions, but getting all the stuff you need to work. The easiest thing would be to find a donor vehicle with the same engine and transmission (and maybe even the same options) that was available and grab the control module(s) and wiring harnesses and hope you don't need to do any re-programming.
I think this would be a big job either way you go. You shouldn't even attempt this without getting your hands on the factory service manual and wiring diagrams. How much time and effort are you willing to put into this?
One of the benefits of modern technology as applied to newer cars is that engine swaps (and even much simpler things) are nowhere near as easy as they used to be, or should be.
Thanks for the input Mikeman, I will take all I can get, I considered what you said and the 4.6 is probably the best solution, though I think only 4wd came with the v8, and used the 4r70w trans, here is my thoughts, if I could get an 04 or 05 crown vic/ grand marq I think I could use the PCM, harness engine and trans and also have a v8 Donner explorer for small stuff. My explorer is the first year without throttle cables ,it uses the drive by wire so I would have to have that. I think It would go fairly good. I see so many failed 4.0 SOHC engines and a lot of cheap gen 3 Explorers out there that something needs to be done. there are also alot of vehicles with 4.6/ 4r70w trans also out there. A v8 2wd I think would be very usefull and fun. I think I could even use the Crown vic PCM w/o reprograming.
Before you go through with this, get your hands on the Crown Vic, Grand Marquis or other donor vehicle wiring schematics and compare those to the 4.6 V8 version of the Explorer. I would strongly recommend the genuine Ford documentation. If you don't want to buy it (I wouldn't blame you), you might be able to find it in your library system.
You need to compare the guzzintas and guzzoutas for the donor and the receiver ECU/PCM and other modules. My concern would be vehicle-specific wiring harnesses. There could be differences in instrumentation or options that you need to consider. The basic engine controls may be the same, but you might run into differences elsewhere. As time goes on, the trend is toward more "integration" - moving more functions into the same box. Initially, ECUs just did engine management. Then they became PCUs and that included things like the transmission and transfer case. I don't know if this is the case with Ford and your Explorer, but I'd want to find these things out before spending time and hard-earned cash. See if the ECM/PCU only controls engine, dash and transmission, or are functions like wipers, climate control, power windows, etc. controlled by the ECU. I'm amazed at all the functions that Ford, and other manufacturers, have determined require microprocessor control.
You really need documentation (schematics and manuals). Without it, you're the proverbial blind squirrel. Maybe I'm being paranoid, but my time is precious and I wouldn't want to attempt this without reviewing all the pertinent information beforehand. And even then, things are never as easy as they seem.
If 2WD was never offered on the 4.6 Explorer, you'll have to also think about the driveshaft.
Here's where I'm coming from. I swapped a 6th generation Accord motor into a 5th generation Accord. The motors were pretty much the same on paper. Only 100 ccs difference and half a point of compression. All the interfaces were the same. Should be simple, right? I stripped the engine down to a bare long block, transferred all the 5th gen parts to the 6th gen motor and, despite all the reassurances from the people selling the motor, I'm having problems with pinging (even with premium fuel). Since the car wasn't worth much, I'm just going to drive it until either a ring or piston breaks or it dies from natural causes. I'm not sure which will happen first, but my preference would be to have a motor that wasn't at risk of damage due to pre-ignition.
I love reading the detail, perhaps I could benefit from your knowledge. I have an 2004 Explorer Sports Trac with intermitent "engine light, no tack, no speedo, no temp gauge". I replaced the differential VSS and it seemed to work well for 1 day. Would you have a recommendation of my next option? Other than the above items, the vehicle runs well, but doesn't register distance. Thank you for any asssitance you may offer.
I have an 2004 Explorer Sports Trac with intermitent "engine light, no tack, no speedo, no temp gauge".
First, start a new thread with your issue, provide more detail if you can and you'll benefit from the collective wisdom here. I don't doubt that someone here will get you closer to resolving your problem or just flat out get you the direct cause.
I would start by pulling any code(s). Provide that in your new post. The codes will give you a clue, but not necessarily the answer. With all things going on at once, look for something common to them all - connector, ground, gauge/cluster module, etc. I don't recall seeing flow charts that address simultaneous issues, but I confess that I have only read relatively few.
I think one of the frequent visitors here has a manual that covers the year of your Explorer. Or try your local library. Without the manual, you're guessing, and even with it, you sometimes are just making a better-educated guess. This is evidenced by the somewhat common fault isolation step in the flow charts: replace suspected bad part with known good part.