I think it is generally the 17" wheels that are the same size front and rear. I had a set of 290s that were all 8J x 17.
The bigger wheels were normally staggered like the 295s I had that were 8J x 18 front and 8.5J x 18 rear. Front tyres were 225/40 and rears were 255/35.
But as B21 says the tyre sizes should be a good clue!