I don't think there is going to be much aftermarket support for development/conversion of the 3.5\3.7 NA. Just because the Explorer is not considered a performance enthusiast market like the Mustang. Those who want performance will go for an Explorer with the turbo and upgrade from there. Since the OEM offers decent factory performance (3.5TT) there will not be a big void for the aftermarket to supply.
I'm sure it can be done but it would not be cost effective verse starting with a factory 3.5TT. The wiring and programming is very intergrated into the vehicle and that is where you will be spending a lot of time on.