My one experience with buying from Mitchell parts was back in the late 1980's.

I bought a set of NOS Hemi spark plug wires.
I installed them and the thing has several cylinders that weren't getting any spark.
There were several bad plug wires in the set.

When I Stopped by their store (during the Mopar Nats) I was told " These plug wires are for restoration purposes for appearance only. They're not for cars that run and get driven. No refunds or exchanges."

The fact that they were sold to me as working plug wires meant nothing to them

Needless to say I never bought from Mitchell Motor Parts again.