I've owned our 1974 Soverel 30 Mk III for 3 years now, and in every respect I really like it, and respect very much the integrity of the design and construction. Very comfortable, safe, fast cruiser. Ours is the cutter version (even tho' now we rig her as a sloop), with shoal draft (3-1/2 ft) and a swing keel, and a Bukh (Westerbeke) 20 hp diesel motor. We cruise the Sea of Cortez, but I would have no hesitation in terms of the boat's design to go on the journey you propose. Other than the standard cruise preparations, two things I would check are: the rudder bearing plate (at the bottom of the rudder), to make sure it is tight; and the swing keel cable, pivot pin, and shackle, to make sure they are in good condition.
If you give me an email address I'll send you pics of our Soverel, since I can't post easily pics from this forum.
Just buying a 1974 Soverel 30 MkIII. Any opinions or information out there would be appreciated. All I have read so far seems to point to the older Soverel models being good sturdy boats. My intention is to cruise out of Galveston Bay and back down to Venezuela. By the way she is sloop rigged and this seems to be the way she came when new.