Updated to better work with more versions of this car, as they all appear to be based on the same model. If you are installing for "M1 Procar '79 (bmw_m1_procar)" then just use content manager or extract to the appropriate location, if you are installing for the "ACL BMW M1 Procar (acl80_bmw_m1_procar)" or "E26 M1 Procar (pddw_bmw_procar_m1)", then you will need to extract the "151" folder from the archive to your skins folder.