When I put new wood in the cab the top part where the sun visor meets the top of the cab is made with a gap about 1/4 inch. What actual fills in the gap and seals the cab?

If I remember correctly there should be a metal header pannel that goes over the wood frame at the top of the windshield on the outside this helps close the gap between the header board and the top. I will do a little more searching and see if I can comeup with a picture of this panel for you. I know my 29 also has a small metal strip on the top edge of the windshield header that help close the gap also.

The gap is sealed with a tar type sealer and then covered with a fabric type welting. It is also used around the joint between the top and sides of the cab.

I knew that someone would probaly know the rest of the info I remember that sealer now that you mention it, what a bear to get the old stuff off.
thanks ChevyChip.