The PCBs for the driver ARE different between 1.5 and 2TB platters, there's a firmware number ,that's the one you may have seen. Not only do the PCB part numbers need to be identical, the REV #s have to match, and the firmware as well. I've seen PCBs for 'same drives' be PHYSICALLY different even though the 'major' part number was the same.
Since you've swapped the PCB and the bad drive didn't come alive, odds are the problem's inside the bubble. It only takes a 240 line program to read it, but odds are you don't know any machine level programmers or guys coding in Delphi. You might try Seagate, to see if they have any. Pretty sure Seagate bought out Maxtor, and one of them had DOS based software that did low level stuff. I KNOW DOS6.22 had the abiilty to read any harddrive,used to use it to locate backdoor codes, reset copy counters.
There is at least 1 copy of the drive's 'index info'. If the master is damaged, you can simply copy the 2nd one onto it, should be up and running.
Big problem could be what version Windows you're using. Everything after 98 got 'complicated' with 'layers' and restricted access to 'stuff', big PITA
Still trying to figure out how many 1,000s of pictures you have on one drive. Gotta be LOTS !