I often think about an SUV conversion project, my 2004 TrailBlazer was a very popular model as was the blazer before it with many still on the roads today. These body on frame Trucks are a dangerous safety hazard.
I can't find it now, but there was a pretty famous article about SUVs how users wanted to be up high, and have plenty of metal around them, as well as lots of cupholders. The height invites rollovers, the metal makes them terrible at avoiding crashes, and the owners died or were maimed hundreds of times more often than minivan owners. The models compared were the Ford Explorer and Aerostar minivan.
For a long time body on frame SUVs were not tested for safety, unlike the minivans.
So you're better off from a safety perspective with a Crossover SUV or a minivan.
Meanwhile we'd all be safer and more efficient if all the body on frame SUVs dissappeared tomorrow, so making them more efficient keeps us all worried about getting crashed into by an SUVs so people don't opt for the smaller cars in any great numbers.
I had my crossover Equinox in the shop for 2 weeks and the delaership loaned me an HHR, a boxy little minivan-car sorta thing. It felt remarkably like my Equinox in so far as size, seating, cargo and modest comfort, but it was lower to the ground, had way less materials the doors sounded hollow when you shut them. It also seemed peppier, it got around town great and accellerated much faster than my Equinox or Trailblazer both of which have larger 6 cylinder engines. I drove the thing for 2 weeks normal commuting and errands on 7 gallons of gas as opposed to 14 gallons in my Equinox, couldn't guess on my Trailblazer we try not to use it outside of commuting to public transportation and big truck jobs.
So from a safety perspective you should be looking to refit a crossover or unibody style SUV, but from an efficiency perspective you should rethink the idea of an SUV that's towing an extra ton of vehicle it doesn't really need.