So after tinkering for a while I needed to replace the blower motor resistor and the pigtail on the project '71 Riviera. The resistor is a common GM part, PN 500890. It fit's the GM trucks from the mid-70's until the 1988 model year. It's not clear if it is with or without A/C, but I suspect with A/C. The pigtail I used a CarQuest part, PN PTA1284. The shell of the connector is perfect to replace the damaged and partially melted one I was dealing with. It has different color wires than the engine compartment wiring harness. I needed to use the wires that are part of the pigtail to replace the damaged factory wiring, but they can be de-pinned and you could install the factory wires into the shell without an issue. It should be noted that the instructions for the pigtail address the wiring color difference specifically. I suspect that this is because the pigtail applies to many applications and not every wiring harness uses the same colors for each location on the connector.