Anyone know if it's possible to swap the O/D DEFAULT so it is disengaged upon startup as opposed having to turn it off manually,I want to only turn it on when I want it on..

 

It's possible with a delayed, momentary relay.
Connect the relay's coil to ignition-switched power, and tap the hot side of the OEM switch through the relay contacts to ground.

A few seconds after you start the engine, the relay points will momentarily close, signaling the pcm to turn off the O/D.
O/D can still be toggled on and off with the OEM switch.