The original Hitachi Travelstar hard drive that came with your Lenovo T60 had a height of 9.5mm. So practically any standard SATA notebook hard drive (max. of 9.5mm height) would fit your T60.
I suggest you get a hard drive with a greater capacity (500GB or more) and speed (7200RPM), as the price increment would not be that much.
Better still, get an SSD with a capacity 120GB or more, for an extra boost to you aging processor.