Since I am not a expert of any kind I would go with what the manual says. Since I would guess that Ford know more about what is proper for their trucks than I do. I drove mine for manual stated time before towing.

 

I feel you are safe to tow with 500 miles on it. Just dont try to break any speed records while doing it. Towing raises all the temps of the engine, tranny, diff, etc so I think it helps to seat everything so long as you dont get carried away and act like Richard Petty with a trailer behind you. I was just shy of the 500 mark when I hooked a trailer to mine.

In theory, these engines will out live the rest of the truck anyway. Not too long ago saw a 7.3 truck with over 400k miles. Engine was running strong but the rest of the truck wasnt worth puting any money in to.

 

I'm sure he has already made up his mind by now! Well, did you pull it?

 

book says 500 miles before 1st tow then take it easy for the first 1,000. I towed my trailer (8k) first time at 600 miles, gently. that is the best way to break it in.
Past experiences with diesel after the break it run it hard and it will do fine.
08 F250 4x4 crewcab.

 

Before I bought my truck dealer let me hook my trailer up to it and tow it around to see if was going to have any trouble with sway control problems. I drove it for about hour with 30 miles on it to start and no problems yet. 4800 miles on it and year later.