1. A computer implemented method for determining criteria of a donor vehicle likely to contain a non-indexed auto part that is interchangeable with a non-indexed auto part on a donee vehicle, wherein the non-indexed auto parts are not included in an index of interchangeable auto parts, the method comprising: in a computer including a hardware-based processor; selecting at least one indexed auto part of the donee vehicle that is included in said index of interchangeable auto parts; and utilizing said index of interchangeable auto parts to determine criteria that identify donor vehicles having indexed auto parts interchangeable with the at least one indexed auto part of the donee vehicle to utilize the interchangeability of the indexed auto part of the donee vehicle in said index of interchangeable auto parts to indirectly assist with interchangeability of the non-indexed auto part of the donee vehicle, the criteria including at least one of a year designation, a make designation, or a model designation.