The 400F triple tree is essentially the same shape as the 350F in terms of mounting. What is different is how the gauges are mounted and that the idiot lights are different. On the 350F they are part of the bridge that holds on the bars. On the 400F you have the idiot lights and keyed ignition switch mounted between the gauges, as well as the steering lock. Other than that, IIRC, the triple tree will mount to the 350F frame without problems, and the brake assembly as well. The headlight and turn dignal mounts were very different for a 400F, but I believe you can still use the fork ears from the 350F on the 400F stuff. Same fork tube diameter as well, 33mm.