Hi Dave,
Pictures are hard to see what it is your talking about. Let me see if I understand your question. Are you referring to the three screws that join the rear of the cab to the front of the cab that are drilled through that wooden block? And if so, is the metal split at the joint? If memory serves me correct, they are sandwiched/laminated-overlapped at that part just above the wooden blocks? How far are you to removing the entire cab? It may be easier to get a good look at it, less the chassis from underneath? Dose it appear to be a stress crack, or rust-out? Are the screws loose, wood rotted, joint seperating?

I can provide you photos, let me know. Sorry, I have no cabs that are split apart at this time, but one that is clean.

Dale