If you were closer you could swap over with the autobox in my scrapper. That would leave me a spare manual box.
However, I think you would do better looking for an HP24 box out of a 4.6. you'll need new props as well though and the gearbox ECU and maybe even engine ECU as I am fairly certain the auto ECU was slightly different. Obviously there's the different gear-shift too. And then you'll have to chip it to stop it feeling sluggish. All in all, easier to stick with the manual and take up squats and deadlift.