Towing a car with a 3.0?

[GSXRliterbikz]

So I know the towing capacity is listed in the manual, but what have people found is the real world ability of an e53? I've towed a 740il on a full car hauler with a half ton Toyota. According to the numbers, the Toyota was too small for that load. But even though it had 220k miles on it, it towed it like a pro.
I need to go on a 5 hr trip to pick up a 740 I this time.
What say you? Too much? No problem?
My x is an 04 3.0 with 140k. I've changed trans fluid 4 times since I bought it with 60k. Transfer case was done about a year ago. And it has the factory hitch.
Ill be hauling it on a Uhaul trailer. They have the automatic braking systems. So ill have trailer brakes.