Depending on the width of your wheels, 215's should work fine.

Also, per the TireRack's spec for Michelin Engery MXV4+ tires:

195/65R15: 24.9"
205/60R15: 24.8"
215/60R15: 25.0"

If your SRS light comes on a long-straight highway driving, 98% it's the steering-wheel's slip-ring and brushes. My 1988 W124 wagon had the same symptoms, and the slip-ring was worn-thru and lots of brush material.

A very CHEAP fix (parts under $70) takes about 30-45 mins.

You do need some long-handled allen tools and you have to discharge the airbag system by disconnecting the RED connector in the passenger foot-well (I would disconnect the battery ground as well afterwards).

Have fun with that 5-speed!