I ran LS wheels on my '96 for about three years.
The spacers were custom machined out of round stock aluminum to precisely fit the hub and lug pattern on the MN12.
I never had any problems whatsoever - I upgraded to the XR7 7-spoke wheels last spring, so the LS wheels are just sitting around.
I may consider selling the spacers (set of four) and the LS wheel lug nuts, if you're interested.
1996 Mercury Cougar XR7
4.6 - Dynomax-Equipped - Tranny Cooler - 3.27 T/L - 125k Miles