Toddoky

Yes, the 4L60 is shorter than the 4L80 but taller where the extension housing bolts to the case.

The is true only in regards to the later 4L60-4L70 transmissions with the bolt-on bellhousings; the earlier 4L60 with the one piece case have a 4-bolt extension housing like a 700R4 that are much smaller in the same area. These two photos depict the difference in a relative context with both the 4L60 and 4L80 shown installed in a 84 C10 using the same engine mounting brackets and at the same engine inclination angle.

The actual clearance depends on the shape of the body contour and in this case the 4L80 does have a little less clearance due to the location of the step in the tunnel, if the step was 1-2" further forward then the 4L60 would have less clearance since it's taller than the 80 where the two top bolt bosses are in the extension housing.

Rsj78

I know I've found a learning curve with regards to the difference in the cab floor contours between years with 4L60/4L80 transmissions