Amount of ports does not really the main criterion. What matters, is
- Both filers run compatible Data ONTAP versions, so one can access disks taken from another
- Number of disks and shelves and total amount of storage do not exceed platform limit, taken in account of course how many shelves you can connect to a single loop and how many loops you can build (here is where number of ports starts to matter).
If all this is checked, it is trivial enough head swap.