O/D relay wiring question

[Uwe Blab]

I am, what is hopefully, in the final stages of installing a 3-speed transmission with electronic overdrive. The transmission is out of a '55 truck, but I'm putting it in a 1970 C/10. The question I have is regarding the relay. I've acquired a 3-post version out of a F**d, but I'm not sure if it may be what's keeping the transmission from kicking into o/d. It has a connection for the transmission solenoid, kickdown switch, and the battery, but only when the ignition is turned on. I had a 4-post relay, which had an additional connection to the battery permanently, but it was a faulty relay.

Bottom line, should the 3-post relay be sufficient to run the transmission?

Thanks in advance for your help.

Adam