hmm
Appears that the water tanks have had issues, and have been replaced by one where the quarter berth was.
Hard to tell from the photos what other modifications have been made.
The rudder needs a lot of work, but you could make it bigger at the same time using the plans that Bruce King made to do so.
Standard issues for a boat of this age come into play, such as the need to redo the headliner correctly.
Also you can be sure that all of her deck hardware will need to be removed and bedded after having been on the hard for a while in Mexico.
There is some work there, probably quite a bit. The electronics if that is important to you are antiques, and most likely do not work, if they do work your phone is probably more powerful than all of them combined.
The boats themselves are wonderful, and would take you and yours anywhere that you want to go, once they are fixed up.
The water tanks under the floor need to be fixed and that water tank up high and aft of the center of the boat needs to be removed. Get as much of the weight back into the middle as Bruce designed it and she will sail better.
Suitability to purpose, could you sail for quite a while in the Sea of Cortez and have a great time. Most likely, I would inspect that rig very carefully however. There are a lot of pieces of the rig missing suggesting that it needs a complete rerig. (Just starting with the missing lowers is enough to tell us that).
The lights are original, they never worked very well to begin with, so you would need to replace them. Sounds like the sails are pretty beat, or non existent.
Right off of the top of my head, I would say that with about $30k over whatever you buy her for you could have a very nice boat to hit the Sea of Cortez in. Compounded by the fact that she is in Mexico, and parts will be more expensive (I assume that you are providing all the labor, if you are not, then this is not the boat for you, pick something that doesn't need this much work).
will you be able to stand up. Maybe just.... The standing headroom as I recall is about 6'3" so you are going to have to take your shoes off. You will fit on the berths though. We had several friends sleep aboard that were your size they all said they did fine.
The wheel moved to the aft end of the cockpit isn't going to make the boat easy to sail I would put it back where it was originally at the front of the cockpit. That location makes the boat easy to single hand.
The deck is Balsa cored and will have areas that are going to need to be addressed. The addition of some of the backing plates in the inside of the boat, over the headliner hint to some areas that are going to have issues. (The main traveler supports being one of them).
Prop strut looks fairly normal, if it doesn't wiggle around. There is an article I have on here about how to remove it somewhere on this site. The fairing being broken wouldn't worry me all that much though.
I would also get rid of that monstrous Arch. These boats don't like a lot of weight in the ends (None of them do, but the 39's have a fairly fine bow and stern section if you look at the wetted surface profile). That much weight and windage is going to affect the way that she sails. Get the radar on the mast, where it isn't going to irradiate the crew, or if you are short on money, dump the ancient radar and get an ais reciever, most people find these work better for them while cruising anyway.
Judging from the fact that you are looking at this boat I would guess that you are not fat on cash, (who is these days?). I would caution you to think about what you really need in a boat, and see if this fits it. New rigging, new sails, getting some of the problem issues sorted out (The water tankage, autopilot, led lights and fixtures for the interior, rudder repairs, and making sure the systems are correctly working is going to set you back a chunk of money on this boat. Say 30K as a rough ballpark.) Beat down whoever is selling it to as low as you can go, and then do the work yourself if you are able, and have done this kind of thing before. If you haven't then it is going to cost a lot more to have someone else do it, (At least triple the amount!).
They are tough and great sailing a boats, wonderful ride, comfortable, and once you have the 1970's oddities worked out of them, they sail easy and are easy to single hand with a good turn of speed still left in them. (note that even cruising couples are really serial single handing!)
Before you hire anyone to survey it, fly down there yourself and look at it.... For a long look, not just a couple of minutes, be with the boat for a few 3 or 4 hours, and see what you see. Take a ton of photos and send them to me, and I will tell you what I see in them. (Within reason on my time).
Note: you need to look at the mast base, and the metal (mild steel), member that connects the fwd bulkheads together under the sole. These along with the tanks which are also under the sole are areas that there are frequently issues with.
Guy