Fotoman, we have friends with a Marine Trader 34 Sedan, also without a mast.* One of their PO's installed a radar arch to carry the radome, antennae, etc.* which keeps the flybridge deck clear.* Pics I have seen of MT sedans with masts* show them installed in the middle of the flybridge deck, and if you were planning to install a boom as well, you would have a lot of "stuff" right in the middle of the fly-deck.*
FF is right in stating that compression loads would be a concern. You might wind up needing a compression post in the middle of the saloon to transfer the load off the cabintop.
On a broader level, you describe the boat as a massive restoration project. If it's as neglected as you say, installing a mast should be way down on my todo list. If the boat has been exposed to ice/freezing etc. over the years, your primary concerns should be the integrity of the hull, decks,* and house, as well as power systems, plumbing, electrical, etc.** If you think the trawler won't look "shippy" without a mast, and you're concerned primarily with cosmetic issues, you may want to rethink taking on this project.
Postscript:* After commenting here I noted another thread about a TT sedan and the Yachtworld link had pics of a "tripod" mast, which might spread the load, but still leaves a lot of "tripper" opportunities on the flybridge:
-- Edited by ARoss on Tuesday 17th of November 2009 07:52:05 AM