What's your trailer weigh fully loaded? You know the V8s were rated either 5,500 or 6,000lbs towing capacity, right?
I tow a camper that weighs about 4,000lbs fully loaded throughout the summers in up to about 105F, and it handles it just fine with a WD hitch. We typically have the AC blasting in the summer heat while climbing 8% grades and recently got two SUPs to put on top of the car too. Sometimes I will be at WOT in 3rd or 4th for 15 minutes straight without lifting in order to get over a pass. This is my third summer doing this routine and I've never had any sort of failure.
I use some sort of synthetic oil, usually 5w40 or 10w40, with Valvoline full synthetic diff oil and trans fluid. I don't know what the N62 oil spec is but I would err on the side of heavier oil instead of thinner, since your oil will generally be hotter when towing than normal operation.
I do not have an auto or a V8, but that's my experience and it's worth exactly what you paid for it.
