Fortunately, the 737-MAX / 737-8 is visually distinctive from the previous generations of 737.

Or you could just avoid all 737s.

You say that jokingly, but the configurations & carriers are actually part of the model numbers contained in the last two digits (and occasionally letter afterwards) [0].

[0] https://flyingwithfish.boardingarea.com/2010/04/27/reader-ma...