You’re close on the first issue 4070B, part number 8017. It was first issued in 1976 in a one piece, flip top style box with pictures of the Paystar dump and Payhauler dump on the bottom. The first run started out with the air bag setup but was changed mid run of the first run, to the walking beam suspension. The second issue, two piece box, blank cardboard bottom was released in 1980 and continued on with the walking beam suspension. The third and final issue was released in 1996 with a different part number and featured only light gray and chrome parts. So far on the first issues, the way to tell if it has the air ride or the walking beam suspension is to look in the lower right corner of the box top next to the ERTL emblem. If it has a “TM” next to it, it’s the air ride. If it has the the little C in the circle, it has the walking beam suspension. The reason that the air ride was changed to the walking beam is that International Harvester discontinued the air ride on their real trucks. IH didn’t want people building these trucks thinking that the air ride was an option so they made ERTL change the rear suspension. We just had a big discussion on this over in the Facebook MTDG group.