Hi Notwendy,
The Yahoo group "Vintage and Older Kenmore Sewing Machines" has a user generated chart of models and features. Unfortunately your model is not listed. If you aren't a member of that group, I'd recommend joining anyway.
I'm also a member of the Yahoo group "Helping others use and care for vintage Kenmore sewing machines". I searched both sites for mention of 158.75 and found nothing. However, I think sometimes there is even a 3rd digit in the last string of numbers and that may be the part that's causing me to get no hits.