Would be a terrible idea unless you want an all around worse HD platform, no displacement for engine braking, tiny little bores (horrible for heat dissipation), and dismal fuel economy. The 3.0 Hurricane got the worst fuel economy of the 6.2L GM, 5.0L Ford, and itself in TFL’s MPG loop with the off-road variants with the bigger rubber. The spread will get even worse with more weight in an HD. The 5.0 in the F-150 is 15-20% more efficient than the 3.5 EcoBoost in towing loops. Heat management is also huge, a 7.3 liter with a cast iron block blows off heat like nothing. A 3.0 will be making you pull over trying to pull 15,000 pounds up a mountain, the temp gauge on the 7.3 won’t even budge.
Ram is using Cummins new 6.7 Gasoline engine to replace the 6.4 gas from everything I’ve seen from insiders. Should be a good engine, 6.7 liters Inline gas. Will have good grunt and heat management.