'87 is a sweet spot for Japanese built frames. Circuit, Prologue, Tempo, Super Sport & Paramount are all good candidates as are the Miyata and Panasonic offerings. The 560 is actually a very nice 531 bike if you can find one in Ecru. They came with 600 SIS, so 7400 would be a reasonable upgrade.

Not that you'd notice a ride difference, but the Merckx frames of that period tend to be somewhat fancier with chrome forks and stays & many of them originally came with DA 7400. Could be hard to pin year of manufacture down to '87, however, as their serial numbers are more of a general guideline than sequential.