Originally Posted by Iride01

Are you certain the small ring is 42 teeth. I'd rather not sit and count them so I'm leaving that to you. 36 would be more common paired with a 52 ring. But older stuff was sometimes different.

If it is a 42 ring, then a 36 ring will give you some easier pedaling to keep your cadence up. And you still will need to find out what the spec's are on that DR. The model number should be stamped on the backside of the parallelogram. Then you or someone can look it up. Max front difference is one of the specs you'll need to check.

Rings can probably be found inexpensively for that old crank. Though you need to know the PCD or BCD of that crank spider to determine if a 36 will fit. Also just check for entire cranks. Assuming that is a BSA threaded BB shell, then you should have a lot of crankset choices. For me, the 2 piece Hollowtech II cranks are easy to install and work great for road bikes.