The problem with most complete working Amigas when sold is, the new owner decides that the unit isn't enough and needs to be tinkered with and modified.
Original HD setup was sufficiant to operate the unit (like it did for several years).
The external scsi header would have been the route to go when adding more HD space (like it had for years).
If it works, don't f*ck with it....
Now where's that screwdriver?