It looks like two V-8 together to make the V-16, similar to what Falconer did to make their V-12. Given the displacement, its basically two twin-turbo'd LS motors. Getting 2500 hp out of an LS motor is possible, so I'll say that 5000 hp is possible, but its going to come at high rpm and with no durability or drivability.
Besides, DP needs to remain diesel-powered. Just get a bigger Cummins, say a QSK95. Then, your motorhome will pull like a train regards of how big your toad is.