1990 ECSB K2500, 5.7 Auto, 3.73 gears, stock tire size: 13.9 avg, 17.6 best
1991 RCSB C1500, 4.3 5spd, 3.08 gears, stock tire size: 19.4 avg, 20.3 best (only two tanks)
1992 RCSB C1500, 5.7 Auto, 3.08 gears, 275/60R15 tires: 15.1 avg, 15.4 best (only two tanks)
I also have a 1990 RCLB K1500...