If you're going to to hire a trailer, you may be better off hiring both a trailer and a tow vehicle from somewhere like Kennards Hire. Especially if you don't know the towbar rating of the one fitted to your 740 tow car. Also IMO and experience, the Kennards trailers are a lot nicer than U-Haul ones. Hiring a vehicle to do the towing from them also takes any worry about the towing vehicle not being fit for purpose.
I have a 940 AW71L NA wagon and a 940 AW71 turbo wagon, and the Tentacle Car Trailer Oz Edition v1.1. I wouldn't tow a 740 with either wagon - neither wagon has had the reinforcing plates for 1600kg+ fitted - and I wouldn't tow a car with the NA wagon even if it did. The NA 940 was okay towing a box trailer with an engine in it, but it struggled to keep up with the fully-laden 940T on a trip where the two wagons travelled in convoy (@paul0075 drove the NA and I drove the turbo). The Tentacle Trailer is at least 300kg unladen, and boy, the NA wagon was working hard towing just the unladen trailer from the blue slip workshop.
IMO, towing a 740 with a NA 740 over a long distance, especially if it's not at least 2-lane motorway for the majority of the journey, would be slow, painful, and given the unknowns about the towing car's towbars and fittings, potentially risky. Sure, you could do it and be lucky. But then again, I'm an over-cautious, luckless old bastard and I wouldn't.