Sabres of that vintage have a thick plywood backing plate under the deck for the pedestal. If it has deteriorated, it is in boat terms a relatively easy fix and it is sort of accessible.
Sabre 34s, 36s, and 38s have an issue with the mast step. The drain was not well designed and water can become trapped causing rot. Many of these have been fixed by now.
While you will find many knowledgeable sailors here on SBO, the Sabre experts are on Groups.io and the Sabre Facebook Group. If you post this same question there people who own S34s will respond. There are over 1,000 people on the Groups.io board and around 1,500 on FB. Note that I am a moderator on the FB group.
But don't give up the ship here, you will find a lot of good reliable information at SBO and great bunch of people.
groups.io