I can't answer your question; however, if you have a long haul I would try my best to rent a flat bed car trailer that would enable all your wheels to be off the ground.

 

My experience has been that the dolly is less stable feeling, but also you feel a lot less load since it's just a dolly. An E350 I don't think is meant to go on a car dolly. Tacoma might be ok, look at the wheels and you'll see how much it is designed to tow. To me a trailer is safer, the vehicle tends to wander back and forth a little more with the dolly, especially with the heavy end out like that, but you'll have a big truck towing it. I've rented some U-haul trailers that weren't that great either.

 

I may be wrong here, but I think I'd put the front wheels on the dolly and remove the driveshaft.

 

The problem with car dollies for rear wheel drives is that when you tow the truck the rear wheels are turning, which turns the drive shaft, which then turns the gears int he rear half of the transmission.
The problem with this is that the transmission pump mounted in the front part of the transmission which turns and pumps only when the engine is running. So some transmission will burn up the gears and bushings while your towing it simply cuz the rear half of the transmission being forced to spin while there is no lubrication being pumped threw it, like if it the engine and transmission was actually running and driving down the road. This doesnt happen on all rear wheel drive transmission but alot of them.
On a front wheel drive car the rear wheels dont turn anything but the wheel bearings which are self lubed so they are a good one for the car dolly but not rear wheel drives.
As stated before you can remove the driveshaft from the truck so it can not turn the transmission. This would only turn the rear diff that and nothing else which would be ok.

 

Thanks to all for the advice. I understand now that you shouldn't pull a vehicle backwards on the tow dolly because of too much weight towards the rear of the combination leading to sway. So I thought my only other option was to pull it with the front wheels on the dolly and un-bolt the drive shaft.

I then called U-Haul and it turns out it is only $10 more to rent a trailer. So I went with that.

Thanks agian for the help everyone!