So it turns! All of that work finally came to fruition. I was a bit worried about the way the Curtis 1231C motor controller wiring is documented in the EA manual - nothing hooks up to the A2 terminal, which doesn't make any sense to me but EA must have thought out and tested their design.
But what's up with the scraping, scratching sound? Turns out the transmission was actually in gear and the hubs were turning. It sounds great in neutral. And of course when I say engine I mean motor...
Now to do a test with it intentionally in gear. The sound is much better due to the surface rust being rubbed off the brake rotors. When I say I disconnected the throttle linkage, I actually mean I disconnected the shifter linkage. I was moving the gear linkage pivot right at the side of the transmission, so I really don't know what gear I was selecting.
Now that we've tested reverse, we need to find a forward gear to check that the motor is wired to turn in the correct direction.
And then select another gear to confirm forward.
I spent the rest of the afternoon wrapping wires in wire loom and zip-tying up the big 2/0 cables and making sure everything was securely fastened to avoid noises and not rubbing against anything bad. It was a great day. :^)