Tom,
You're right - it's tight!
The Garmin 430 is the longest thing in my panel, and I managed to fit it in. First, if you're planning on flush-mounting the faces, you might rethink - that will by you about 3/4". Next, when laying things out, make sure that you put the long stuff high enough in the panel to miss the forward gear-box top cross brace. Do these two things and the 430 will fit - just!
Paul