I watched a segment on CNN on this this morning. It showed ol' Pat there with 10 45lb weights on each side of the bar bell and he pushed it up and down in "mini-presses" several times. That's 900 pounds of weight BUT his range of motion was only about five inches. To truly be called a leg press and qualify for a record, the extension would have to go from where his pelvis was on the same plane as his knees and then to a fully locked-out position -- knees locked, legs straight.
CNN interviewed Mr. Natural Universe and he did 10 reps of 1,000 pounds at a much greater range of motion then ol' Pat there and that was all that Mr. Natural could do.
The machine that would be required would have to be specially built for the event. The highest standard weight that gets put on a bar bell is 45lbs and it would take 44 of them puppies to get up almost to a ton. There isn't a standard bar bell that would take that stack and not bend in half.
I used to power lift in college

I'd love to see ol' Pat pull this one off!