Thought I'd add share my install steps I was intending to use the hardwired version of this decoder, but got the 73100 to see first hand how it compared in size, and to see the potential of other installs. There's a lot of potential for shorts with this board, if you're not very careful. Make sure all contact points are shielded, where need be. I fried the first version i had, not even sure how. But, this time I was VERY aware of all contact points. You can see here the size comparison with the Kato Mech. There's plenty of spare room in there. I cut out the rear of the unit to house the speaker. I could have taken a little less off, but this thing is decently heavy even with the extra taken out. This mechanism has a really tight way of connecting the motor tabs to the power tabs, and initially I went the the version I think most do, just taping off the tabs to isolate them. Then someone suggested an alternate way to run the vertical tabs up, by cutting slots further inward in motor mounting container, Like so... Then it's just matter of hooking up the power, motor, and speaker leads. The SMD forward and rear headlights don't apply in this situation, plus I'm a really big fan now of putting the lights right in the headlight housings. I just really hate the lit-up cab look. I used the F/R leads, and remapped the function of the rear light so use as one of the headlights. But, you could just as easily use one of the Aux connections That's it. Pretty straightforward, as long as you don't fry the first one, have to find someone to reprogram the new one, and start the install again.