Have to agree with OLDani, Im afraid. One thing I have learned over the years is to never buy a used converter unless you know the guy real well and the car it came out of.
Nothing will pi** you off more than buying a "good used converter", going through all the work to install it, driving 2 hours to the track, and finding out the converter is junk....
Buy one from a known manufacturer. Call several and ask them for their recomendation for your vehicle.