I would be very surprised if G-IPRA only visited AMS once or twice... G-IPRA I remember seeing quite often... It's in my log for 1985-04-04. Searching for it in the forum yields 2 more dates:
17-11-1984 and 18-3-1984. (YS11 obviously logged it before I did)
G-BJSY I do not have in my log, which hints (but nothing more) towards not being a frequent visitor. This can also be found twice in the forum:
28-6-1987 and 29-1-1986.
Are you looking for a single day on which both a/c where present?
Incidentally, G-BJSY is stated as a Beechcraft C90 King Air, which is of course a descendant of a Beechcraft 65, but quite a bit more modern:
https://scramble.nl/database/civil/details/beech_4822
Regards,
Robert W
"In the beginning the Universe was created. This has made a lot of people very angry and has been widely regarded as a bad move."
Douglas Adams