I have done this on my truck. I have a 2003 SOHC 4.0 . All the parts were factory off a 04 Explorer ' flex fuel '.
The problem I can see you running into..
1.) If trying to use factory parts, converting to a returnless fuel system.
2.) If going to an aftermarket/self inventive system, having to find all the parts/materials.
Its is VERY ' do-able '.
As for ' being less efficient '.. I'll say ' hogwash '. Others will call out all forms of reports and studies BUT, those studies speak of factory programs on an engine that uses both gas and E85 in a mixed variety.
Many people here use ' tuners ', ' flashers ' or ' programmers ' and see gains in their mileage. The same can be done for ethanol.
I don't have what one would call a ' factory ' motor. Its been milled and built a lil'bit . With the present setup I have, I see no mileage difference between E85 and Reg87 gasoline. I average about 12mpg in the city and 15 on the highways.
I will say that E85 gives a better Pull when the throttle is mashed. I've tested it at the local 8th mile specifically. I wont post numbers BUT, E85 landed in the middle of my timeslips with 93oct gas being the slowest and 93+Nitrous being the highest. .300 of a second was taken off my 93oct gas times. Not bad for just ' switching fuels '.
I tried Nitrous and Ethanol together once against the judgement of a local dyno shop. They had my truck for a while afterwards ' straightening things out '. Something about a burned piston..
The optimal setting is to be able to go ' both ways '. The 3.0 rangers that are ' flex fuel ' are a perfect example but the setup isn't designed to be more efficient with 1 or the other. Its a balance of both.
I'm limited where I can take my truck. I can get Ethanol from local places, but If I were to go to a meet in Detroit like I used to.. I would be.. Hard pressed to make it home as theres no suppliers in that area.
Once availability becomes more wide spread.. I'm sure the marker for conversion kits will come along with it. Presently when I do go to a bone yard, I look for those explorers for their axles and fuel systems knowing someone will want them.
As for my conversion, it took me less then 3 hours. I would say if one is familiar with tools and has had a hand on their engine before, it shouldn't take long at all.