One thing to consider is that the 5.7 has roughly 140 more hp and gets 1-2 mpg less (according to the EPA) than the 3.7
If you wanted an extra 140hp, you could spend a lot of money for a one off kit that might work, would require a ton custom fabrication, and might come close to the long term reliability of a stock motor. This is assuming that it would be possible to nearly double the stock horsepower without serious upgrades that come with boosting a motor. These would include head studs, extra fueling, most likely intercooling of some kind, getting into forged internals, and some sort of a fuel management system, either piggyback or standalone.
Assuming you could get all of this done for the same amount of money as selling your 3.7 commander and buying a 5.7 commander, which I find highly unlikely, you would be left with a high strung motor with a lot of custom parts that would most likely need to use premium fuel, would probably get about the same mileage as the 5.7, and would be much more difficult to get serviced if something did go wrong.
If it were me, I would sell my 3.7 commander for what I could get for it, and assume I would have to throw another 3-4k to upgrade, and possibly get something with fewer miles/more options, and have a nice, stock, reliable, servicable engine that happily runs on 87 octane and wouldn't scare off prospective buyers when I eventually sold it.
If it does get done, post lots of pics, because turbos are cool.
Last edited by briman2021; 11-23-2016 at 03:40 PM.