Just 6 years ago, I found myself looking at EXACTLY these same boats. My interest was in either an Alberg, Triton, Vanguard or Bristol 30 or 32. I did much research (sometimes hard to do on these older boats), and 5 years later, found a deal that I couldn't pass up on a Bristol 32. My desire after research leaned more toward the West Coast version of the Pearson Triton since these boats are complete fiberglass, no balsa core but it was a little too small for our requirements.
I was happy to hear several people tell me that fiberglassing was something new to boat building in the late 60's and early 70's so these boats were being built more to wood standards and with fiberglassing being done on the side of caution, these older boats were built like tanks. After the survey I had done on my Bristol 32 (1972), the surveyor said he has never seen a better hull on ANY boat!
You will often see these older boats in the back of boat yards with winter covers hanging in tatters and dirty from the exposure with an old For Sale sign on them. If you can find the owners of these old boats, I am certain there are some very promising vessels out there. Yachtworld and Usedboats.com are littered with these boats. Don't forget to do a search on For Sale by Owner boats. That's how I found my boat!
Best of luck.