Well, it AIN'T a simple "toss the truck" modification. Be prepared to (1) lengthen the frame a bit (2) modify the "3rd" truck bunker into a new bunker over the rear truck (3) a good bit of whacking and cutting to make it look OK. The frame extention would need to be pretty "beefy" because of the weight and size, possibly made from brass or some other metal. The trucks are self-powered so the electrical mods would be probably minimal.
Be prepared to possibly mess up an expensive loco if you aren't sure of what to do or have never cut up and butchered such a machine. I am sure there are those out here (or on another site) who have done this so it is a do-able thing.
Na Wood ie, you didn't scare me off. I'm sat here looking at the 3 truck Shay. The tender on the loco itself is quite large,I would have thought I could get a speaker, the dcc board and sound module from the rear tender and put them in. I think the big problem (for me) is stopping the rotation of the final drive, do you think it will just saw off.
anyway, once the festivity are done with I will open it up and have a good look.
yes, I would like to do a straight swap for a 2 truck, but there doesn't seem many about.