No.
The main problem is the ignition switch, located down at the left on the 350 and up at the triple clamp on the 400. I think the idiot lights are quite different too but that should be relatively easy to sort out.
I don't think there are any other severe differences but I have never set them side by side to see. Since the 400 ignition switch is further along the harness you could maybe cut the wires at the connector and slit the sheath near your switch then fish the wires out?
I have a 400 harness loose, if you want I can lay it out and get a picture for you to compare.
