It can be done, we have done conversions as well as stand-alone engines for RestoMods of nearly every generation in some form, including Gen-4. That being said, it would be quite expensive to do what you are asking from an engine management and retrofit standpoint- it would likely be more for that end of it than the engine itself.
IMHO, I would look into our VS-X700 instead. We can install on a Gen-2 on request. It would give you the look of the Gen-4, more power than a Gen-4, the most important technology aspects, and done in a package that absolutely trumps the Gen-4 in the visual department- at least for stock appearances. Look at my avatar to the left for a quick reference as to what I mean.