My corolla with factory gearing/tires runs around 1600rpm @ 45mph, at 40mph it down shifts out of lockup
. Camrys are about the same with a 2.2L but shift out of lockup at around 45mph. My dad's "low geared" 1987 4x4 Mazda pickup (2.6L) runs around 3200rpm @ 70mph (~1830 @ 40mph).
Never comapired rpms before, but it seems like ~2500rpm @ 70mph is pretty ideal gearing for a 4 cyl.