If you find time and if this helps, here’s a short Avisynth script to put one, or the other, or both numberings on the frames. If iMovie can import/handle .avs files, you could watch it from your timeline. Otherwise, you might be able to view it in a videoplayer:

file name (completely arbitrary): THX_numbered.avs

##=================
## video w/ frame numbers
##=================

## Video path & name
## ----------

movie = "THX1138_35_stabilized_HD\THX1138it.mov.mp4"

## Get video & enforce format
## ----------

film = DirectShowSource( movie )
\ .ConvertToRGB().ConvertFPS( 24 )

## Add counters
## counters slow the display
## remove "#" from only the one to show
## ----------

#film = film.ShowFrameNumber( x=100, y=50 ) # frame number
#film = film.ShowSMPTE( x=100, y=75 ) # SMPTE
film = film.ShowFrameNumber( x=100, y=50 ).ShowSMPTE( x=100, y=75 ) # both

## Display
## ----------

film