Welcome to SBO. Which boat should I buy is a pretty common question for newcomers to the sailing forums. You will receive a lot of suggestions.
The answer to your question about using weight as a criteria is a question trying to simplify a decision. Weight is an easy criteria to use, however, it is only one small factor in how well a boat sails and which boat is most suitable for the kind of sailing you intend to do. Hull design is as important or more so than weight. Live aboard space is also important.
To put boat design into perspective, the 80s were an interesting time for boat builders in a lot of ways, including financial, but that is another story. A lot of boats were built to criteria established by racing authorities, in the 80s there was a transition from following the CCA rules to the IOR rules along with the beginning of what eventually turned into sport boats. A fourth design thread was the beginning of "dock condos," boats built more for comfort at the dock than sailing ability.
The CCA design boats are very traditional looking, have full or semi-full keels and narrow beams. Typical designs came from Carl Allberg, Allied Seawind, and Cape Dory among others. These are fairly sea kindly boats for their size and tend to be a bit heavier than other boats of their size. They will be a bit slower than some of the other designs. The hulls tend to be more V shaped which along with the longer keels allows them to track straight and ride waves a bit more comfortably.
The IOR boats tend to have tall masts and big head sails with fin keels. They are a bit beamier and quicker than the CCA boats, however they can be a bit squarely under a spinnaker. Interiors are a bit larger and more comfortable, these were often marketed as racer/cruisers, boats to race on Wednesday evening and cruise on the weekends with family. There can be more variation in hull design here than with the CCA boats. C&C, Sabre, some Tartans, Cals, and Pearsons are some of the brands that fall in this niche. These boats had fin keels which improved up wind speed and pointing ability due to the keel shape and reduced wetted area. Hulls with more of a V shape especially in the bow can be very comfortable boats in most conditions. Boats with flatter or U shaped may be a little faster off the wind but will tend to pound going up wind. I had a Sabre 30 for a number of years and it was a dry boat that handled sailing up wind in a sea with out pounding.
A third style emerged in the 80s, the club racer. Pearson Flyer's, Tartan 10s, J30s were among this group. These boats were light by design often with a cored hull. These boats were designed to do well on the Club racing circuit with good upwind and downwind performance at the price of some comfort in sailing. They can pound going upwind and be wet. In my younger days I spent a lot of time sitting on the rail of a J30 and Pearson Flyer. Neither were ever a boat I wanted to own.
Finally there was the emerging category of "dock condos," boats that were designed and built more for comfort at anchor or a dock rather than their sailing ability. Often they were large and beamy with plenty of room for entertaining. Since dock condo is a somewhat derisive term, I won't mention brands or models. You'll know one when you see it. Some of these boats were sold as a "lot of boat for the money."
For your intended use, you'll do fine with boats in one of the first two categories. One that has been reasonably well maintained and speaks to your heart. Learn some more about hull design and pay attention to that more than weight alone.
Good Old Boat magazine has a feature in each issue where an older boat is in the spot light. Part of the feature is a review by Rob Mazza a naval architect who was part of the C&C design team and has worked at other firms.
Sailing magazine also reviews older boats, another good source for information. And there are no doubt more informative article on hull design available online.
Good Luck! Enjoy.
