I suppose it depends which Europa they are racing. The S1/S2 versions came with the same size of tyres F/R, the TC had wider rear tyres to compensate for the weight distribution I believe.
Assuming an S2 with standard 155/80x13 wheels, then your 205/60x13 is a good comparison on diameter so the speedo is going to be about right. 185/60 is going to be smaller although I doubt you'd notice it unless someone told you. 195/50x13 is considerably smaller than 155/80x13 and even 185/70x13 so there's going to be 10% or so in speedo error on top of what it's already at.
The plus side is that it will fractionally lower the car and of course stiffer sidewalls feel different. You may or may not like the increase in stiffness, just depends your roads and driving style.
Personally I had 185/70 and 175/70 when I had 13" Cosmic wheels. I now have 15" wheels with 205/50 and 195/50 which approximate to the original sizes on my car (TC). I think you should get away with 195/60 on the front if you wanted to, clearance on my car is tight on full lock but it is enough to miss the bodywork.
Run it through a tyre comparison page and see what you think, this is what I've just used and it gives speedo errors as well
https://tiresize.com/comparison/Brian
