No one knows?

Well these trucks are approaching 100 yrs old.. Its probably harder and harder to find the answer.

This subject is crossing the older thread but different so I will explain what I am doing. I am custom welding an old seat frame to fit bc I didnt like any of th alternatives and this cab is small.. front of the seat is only 43" width.. back wider.. anyway once I add the foam and put it together; not sure how Im gonna attach it to the tub base on the '38.. maybe drill holes and hog ring it.. but really curious how they did it factory!
