Thanks for adding the link. Your right the regular SPDT relays are way easier to get and can be wired with regular lug connectors if you don't have the relay socket. That is how I originally wired my car.

The VBA-1001 connector shell is unique, but the connectors are fairly standard lug connectors, very simular setup as the bulkhead connector, the lug connectors just snap into the shell, no special crimping tool required.

If you buy the 'T' connectors that mate to the motor/switch connector it makes the installation nearly a simple plug-in deal with the only other connections needed is to attach the ground wire and to tap into the +12 volt yellow power wire.

Also looking at the photo of the dual relay setup, the 87a wires should be larger gauge as they have to handle the same current as the +12 volt side.