I can tell you that my 80 drove like a race car when it was stock. After OME 850J / 863 lift and 35’s it was a complete nightmare. Negative 3 degrees caster measured at the driveshaft flange. Offset bushings got me back to 0 caster but the truck was still a terror to drive. I went back to OE bushings and Landtank 2.5” plates and my caster is now 2.3 degrees. Truck drives okay but I wish it were better. Based on my lift, I am in between 2.5” plates and 4” plates. I should have gone with the 4” plates, but they require a double cardan front shaft and I didn’t want the extra expense. With your truck being part time, you could easily get away with 4” plates and no double cardan shaft. Win-win.