someone that understands the ps3 system better than me can confirm or deny this.
with a pc when you want to transfer from one hdd to another, you have to make an iso image of your hard drive(an iso is an exact image of your harddrive, exactly how everything thing is arranged, not a "copy") then write the iso file to the new hard drive. if you just go into your C drive and copy everything over to a new hard drive this wont work as some files cant be copied and there is some data in the formating of the drive that wont be carried over, so instead you make an iso image, which is a copy of the drive not just the files
i think this should work with a ps3 as the new ps3 wouldnt know the difference. and the gt5 save would think its in the original ps3 too