Catalina didn't make a bad year in the 27. There are various trade-offs that have been made over time, but these vary within years of production even. So, don't worry about the year. I prefer earlier boats because they tend to be overengineered. In early production (with most makes), fiberglass was not as trusted, so manufacturers tended to err more on the side of adding too much. This makes for a heavier boat, but one which will theoretically wear better.
I have a 1972, and as you mentioned, none of the deck hardware has backer plates or any other sort of reinforcement. It really disturbed me at first until I noticed that in 40 years there hadn't been a problem - not even any spider cracks to speak of. Then, the first time I had to drill a hole in the deck I realized why this was so. The deck is damn thick!
As Doug points out, it's all about the boat's history. My 1972 had been neglected for several years, but was built well enough to tolerate a certain amount of that. After a thorough cleaning and some new running rigging, she was ready to go. She's a very solid boat now.
My advice is to ignore the year and look at the boat. If cared for reasonably well, the first boat produced should be every bit as sound as the very last one they produced. If neglected, they're both best avoided. Look for a good deal in whatever year. But, make sure you get a haulout done so you can look at the keel. Provided there hasn't been trauma and there are no soft spots, the hull and deck are the last things you need to worry about, but you do want to get a look below the water line.
Things that you do need to worry about is pretty much everything else. Any bargain boat is going to need hardware rebedding, a good cleaning, and probably new sails and/or other running rigging. But, when you start to get into replacing standing rigging or making deck or hull repairs, it starts to drift away from the "bargain" category.
Also, pay close attention to the engine. This is what bit me when I bought a bargain boat. I paid $3500 for the boat, and felt like I knew exactly what was wrong with it and what it would take to get it up to the condition I wanted. I was almost dead-on with my assessment except that I overestimated the condition of the motor and underestimated the repair-vs-replace calculation. I ended up dropping over $4000 on a new motor (with bells and whistles), and after a few thousand dollars in other repairs/improvements (which I HAD budgeted for), I couldn't sell the boat for what I've put into it. If I had been smarter about the motor, I actually could sell the boat for a small profit otherwise.
Though ... you should really never do the math.