I have been doing a conversion also. But it stalled as I decided to change the outward appearance of the loco. Here is what I’ve been doing with mine…
I am installing a g-wire/Titan in mine. I also installed a USA Trains smoke unit. I hope to take advantage of the puff driving ability of the Titan to get puffing smoke.
I installed a small speaker in the smoke box in front of the smoke unit to take advantage of the Titan’s stereo sound.
I installed a simulated fire circuit from these guys:
http://www.modeltrainsoftware.com/fire-led.html
To get the firebox flicker.
Like everyone else, I gutted the old factory boards. I put the batteries, Titan and G-wire in the tender. I installed 2 6-pin connectors to run wires from the loco to the tender.