Locating a set of Saleen Mustang AREs (mesh or 5-spoke) or even a set of 17" Saleen Speedlines would be easier.
The Ronals are an aftermarket wheel like all the others. Meaning wheels spec'ed for different makes. There's probably a set a 16" R9s, with a 114.3 lug pattern, featuring the correct widths and backspacing for a Saleen Mustang, somewhere out there.
The R9 is a heartier (=heavy) wheel than the ARE copy.
If you're looking for a set of Saleen production wheels, either be patient or start looking at classifieds for a rundown 1984-1986 Mustang SVO. AREs, DPs and Speedlines are mounted to some vehicles out there. Even a spec set of R9s can be found now and then.
85-0001, 86-0088 had Ronal R9s and the black hatchback in the '87 Saleen brochure had R9s as well (for the photo shoot).
Anyway, no. Don't buy wheels off of or spec'ed for a Mercedes.