For ****s and giggles I found dump graphs for the stock 4.6 and that 1.8t. Wanted to see how they compare and at what rpm’s. if your towing a trans with a lower first gear would be better for starting out.

Or a transfer case with a higher high range ratio would help too. You could also ditch the stock transfer case and pull a whole setup out of another truck from a scrap yard. I’ve done quite a number of engine/ driveline swaps in the past. All fun to do and even better to drive afterwards. Most rewarding one was a 5.0l roller cam motor I converted to carb and installed in a bronco2 with a c4 tranny. Lots of custom work. Made all adapters myself. Second was a 460 into an f150,

 

How about a 3.0l Jaguar/Range Rover Sport V6?

 

I'm a Toyota and Ford guy, but the GM LS engines are hard to beat.
Dependable, long lasting, and really great gas mileage for a V8, especially in heavy vehicles.
A friend of mine bought a remanufactured LS3 long block last week for his Silverado.
It came with the oil pan, timing cover, and lower intake too.
$1200 with a one year, unlimited mileage warranty.
That is a hard deal to beat! Especially adding to AceEngineers swap kit.
So roughly $5500 in a new LS engine D2 swap, that should go 300,000 miles.
No way I'de spend time and money on a turbo 4 cylinder or V6/straight six over that.