I saw a truck like you describe in Hutch at the convention this year. May be the same guy. Those things were actually offered by Chev as oem for a couple of years in the mid 50's but they became obsolete in a hurry when Eaton and Timkin came out with through shaft bogies. Hendrickson walking beam suspensions must have been around in the 40's because I have some old Batco catalogs that list them and they look like there were very little changes from the 40's through the 60's. I just got through scrapping an Eaton 3 speed on a Hendrickson that had hydraulic brakes. I thought I was lucky to get $100 from a scrapper who winched it out of the weeds.