My good friend owns a late 70's O'day 25 swing keel.
He paid $5500 (the asking price) 2-3 years ago and it came with a trailer that was in good condition.
The boat looks to be in similar condition (from the photos).
His came with a secondary roller furling for a genoa that does not use the forestay.
The engine was a Zephyr sail drive.
Old depth finder and VHF.
So I would say that you might have some wiggle room.
As I said, he paid the asking price, but, he refuses to try and negotiate a price on anything