I'll start out by saying that I don't know of a particular tweak that does that on the iPad (3 or otherwise).
I actually have used that particular lockscreen theme on my iPhone 4S. So, naturally, I tried it on my iPad3 (cause I like it .... and I could ). The lockscreen background didn't work quite right. If I remember correctly, the lockscreen on the iPad3 looked like an iPhone screen (the upper corner of the iPad had the picture, while the rest of the iPad had a blank screen). I believe that it's a matter of coding either the HTML files or the files that make the clock/time appear.
TBH, I abandoned the project because I got involved in other stuff. But - maybe you can take that tweak and modify it to fit the iPad3? Sorry, but all I got is reminisce.