If your going to get a block(6.4, Hellcat) go 426, 4.05 stroke with the 4.09 bore, and don't look back. As for cam inertiamotorsports.com tell these guys what your looking to do and they'll help you with a good tow haul cam.
I have 426CI 6.4 with Eagle heads in my 2014 ram right now, , pulls like a V-10 , gobs of low end break stuff type pull.
I had 392 with eagles and a SRT 392 Auto cam in it, ran great but no bottom end, the cam didn't like that off idle pull, even with the stock Eagle intake.
So the 6.4 with a SRT 6.4 cam didn't have TQ but the 5.7 you swapped on into did? If towing was my only goal I would probably use the eagle cam and heads on the 6.4 short block. My 2011 5.7 tows my open car trailer with a mid size car on it pretty awesome, I pass 12 valve cummins trucks with similar loads on the big mountains around here pretty regular. It does need to turn more RPM but so what, it don't seem to hurt anything and turns in 13mpg while towing on a regular basis.
