The photos appear to be of a deck from Hughes 38 (AKA Hughes Northstar 38) or a similar S&S design. These were built in Canada in the 1970's. The interior clearly appears to be a wooden hull with race boat framing from the late 1960's or early 1970's. If I remember correctly this appears to be a very similar design to P.M. Edward Heath's Morning Cloud 1.
The perferated frames was sometimes used as a weight savings move in that era when wooden boats were still seen as being potentially lighter, and stiffer stiffer and also stronger than similar weight glass boats.
I do not believe that the Hughes 38 or any of the S&S 38's were available as a yawl. Given the lines of the boat, and if she was every actually rigged with two spars, then more than likely the intent was to rig the boat as a yawl and not a ketch.
When you talk about restoring an old boat of this era, it is not something that should be done lightly. Adding or subtracting weight will impact how the boat will actually float, and how much stability it will have. When it comes to structure and hull thicknesses, you want just enough to make the boat strong enough that you can sail the boat reliably. Randomly adding structure can only negatively impact the boat's sailing characteristics, carrying capacity, and safety.
My point here is this, if you were an experienced boatwright, and if you had access to a good yacht designer, restoring a boat like this can be done and end up with an okay (or slightly better) boat. It would mean rigorous reverse engineering of what you have and then careful design to produce what you want when you are done.
But you show not even the slightest sign of being experienced, or rigorous in your approach. Your basic descriptions of what you have show a general lack of knowledge of what you have bought and the process required to get to a finished boat. Its not for me to say this since you probably know this already, but sometimes it is helpful to see this in black and white, you basically have three choices here: 1) Stop for a moment and do some careful homework. Learn about the boat you bought in real detail and develop an engineered plan for your work before you do any more harm to the old girl, 2) Roll the dice and hope for the best. Having designed a few boats in my day and read your post, I respectfully suggest that given your approach and knowledge level, the dice are loaded against you at this point, or 3) Realize that rebuilding a derilict is not for everyone and that buying this old hull was probably a mistake that can be reversed by getting rid of these parts of a boat one way or another, and while that may prove expensive, it would not be as expensive as blundering ahead.
And if you are considering continuing with plan 1 or 2 you need to bear in mind that a hull, old engine and some rigging represents perhaps 20% of the overall costs to rebuild a boat. The material and labor to properly rebuild and upgrade an old boat of this size to a yacht level of finish can easy run $80- 100,000, of which the labor is about half.
And if all is done with a high level of skill and attention, and the boat was in perfect shape, if it has a really clever layout and perfect finsihes, and a like new engine, and great sails, and good deck hardware and reasonable electronics, given the limitations of the dated hull design, it might be viewed be a moderately nice one-off with a value somewhere in the $20-30K range. Those are huge "if's".
As John points out, you can buy similar boats ready to go for far less, get out there sailing sooner, and have something which would be easier to sell when you are done with her.