Sure.
I stripped the DC light board of it's LED's and resistors and used the front LED contacts on that board as the solder point for the decoder input leads (middle arrows (green)). Aside from having to solder the decoders motor leads to the motors own input leads (red arrows), this is what I mean by "practically drop-in".
The only destructive modification required was to cut the rear light tube short to allow room for the speaker, and sever the ditch light tubes from the headlight (red lines). The aux 3 and 4 wires lead to the two ditch lights which are epoxied in place to the frame in line with their location on the shell (front green arrows). [mini rant] I just hate the idea installing LED's on/in the shell, thereby keeping the shell on a leash, and especially don't like trying to fold and tuck wires into place
while installing the shell. So whenever possible, this is the way to go.[/mini rant]
Anyway, pictures:


