Just letting you know I did a similar conversion on my vintage Mercedes recently, with no problems, for about $57 (for 20 studs).
I used ARP wheel studs meant for Hondas. I ordered them from Summit Racing (mostly American car drag race stuff, very similar to Jegs). SummitRacing.com $12 for a set of 5, and very good quality. Their website makes it easy to search and sort by thread size, length and spline diameter. Plus, they were in stock, and were shipped and at my door in a day or two.
With the M12x1.5mm thread size, you have many options, since even newer American cars use that size.
(And, it's fun to tell Mercedes purists that my car has Honda studs!)