The small LEFT terminal should have continuity to 'ground' (bracket) with resistance.
That will be the 'S' terminal, or Starter Activation terminal.
The small 'Lite Blue' wire connects to 'S'.
The other small terminal 'RIGHT' will be 'Open' until the relay engages.
This is the output to 'Hot Wire' the ignition when cranking the engine to help with cold starts.
It's usually labeled 'I' terminal.
The 'Small Red' wire connects to that 'I' terminal.
The large lugs don't care what direction you connect them,
But remember, the smaller wires with large ring terminals all connect to the battery cable side of the relay, which ever one you decide to designate as 'Battery Cable' connection.
The other terminal will have single cable to starter motor positive terminal.
There are TWO types of automatic transmission relays,
One has three terminals,
One has TWO terminals...
Since you have verified ground of one of the small terminals to the bracket, you have the standard 'Ford' type of starter relay.
The one that has two terminals won't be marked 'I' and 'S',
And 'Power' for the relay will be the same,
But the relay ground will be the second small terminal, which grounds through the Neutral Safety Switch on the transmission.
(Usually with the Chrysler Automatic Transmissions)
The Neutral Safety Switch for THM 400 Transmissions is on the steering column, and opens the 'Activation' or 'Lite Blue' wire as near as I can tell from the diagrams.