1. I recently "standardised" all the 4 regular wheels with bolts of equal length. Costed me RM100 (approx USD30) for a set of 4.
2. The spare tyre uses a shorter length of bolts, and not the regular.
I found that out the hard way. Since then, I have the extra set of spare-tyre-bolts. Same for the W126.
However, my brother found it more convinient to have all the same wheels and dont worry about the shorter spare bolts.
I guess its the nut behind the wheel that matters?
ps. its costly to purchase just one wheel.