Non drive has diamond with 3 inside.. Drive side has circle with 0
Right hand crank is 1980, which looks in amazing condition. Left is 1973.
The modern seatpost is with a metal refinisher to be polished to remove logo,s
Not a purist choice but nice and light and I like em..
I'd think you would have no choice but to use a modern one, or maybe an old MTB seatpin. Your frame is actually too small. The amount of exposed seatpost as it is now is probably longer than the whole length of an old seatpost.
I would put the date a bit later to around the mid 80s or later, because of the allen key brakes, under bb cables, full sloping crown. A 1980 frame would more likely to have over bb cables, nutted brakes and a semi-sloping crown.
A couple of other things: the tubing sticker is much older than the frame, and the bb looks quite high.