Almost thought your post was a troll, but given your example of a Triton, I'm leaning toward good faith.
There were a number of very well built boats made before the 1980's, and as the previous post mentioned, it's more about how they have or haven't been maintained that can make or break 'a deal'. The diamonds are diamonds, and yes, you might get lucky, but if it's 'a deal', chances are you'll get exactly what you pay for. Let's see, off the top of my head, here's what's on the list:
Rangers (23,26,28,29,33), Yankee (26,30), San Juan (24, 28, 29) Pearson (Triton as mentioned, 30, really a number of different ones here) Morgan (there's a well sailed 27 here locally that does well under phrf, and again, a number of others like the 38, etc...) Irwin, Tartan, C&C (anything from 24 to 61) Swan (36-65... the ones in good condition will still be pretty expensive. There probably weren't any boats of any
era that were better built. For example, the original 44 sold for about $48,000 in 1974. A good one will sell for around $160 - $230k) Hinckley ( pilot 35, B-40... again, good examples will still be expensive. . And let's not forget one of the ultimate plastic classics, the Cal 40 (20, 25, 34, etc... still many sailing. The Cal 40's still have had a one design fleet for PacCup, and TransPac in recent years) The j-24, love'm or hate'm, dates from 1977, sooo....) There are many others not mentioned for lack of time, but a look around many marina's, and you'll find a number of well cared for boats built before 1980. Just remember, a build date is just a date. It's all about how a boat's been cared for over the years.