The distance of the Sun and Mercury
Assuming you mean the distance from earth to the sun and earth to mercury, the are as follows, according to Wikipedia: The mean distance from earth to the sun is 149,597,890 km.
The mean distance from mercury to the sun is 57,909,715 km. Extrapolating, by subtracting the two distances, one gets 91, 688, 715 km as the mean distance from earth to mercury assuming that the planets were in alignment on the same side of the sun.
However, with mercury on the opposite side of the sun from earth then the distance from earth to mercury would increase by 57,909,175 km over the earth's distance to the sun to 207,007,965 km.
I hope this helps you with your problem with the 1987 Alpine V6 though I can't imagine how.