This one you would probably have problems with in an 8591A. This was a modified FM Demod board that was for DECT (8590E Series Option 112). This was never available for the 8591A. It shouldn't hurt anything to try it, but it may not work quite as expected, or it may be very confused...
Of course, you would also need the speaker assembly, rear panel earphone jack, and wiring to the front panel volume control.
This one you would probably have problems with in an 8591A. This was a modified FM Demod board that was for DECT (8590E Series Option 112). This was never available for the 8591A. It shouldn't hurt anything to try it, but it may not work quite as expected, or it may be very confused...
Of course, you would also need the speaker assembly, rear panel earphone jack, and wiring to the front panel volume control.