How much could you alter the film if Abraham Zapruder had shot in slow motion mode?

[David Healy]

This video seems to say that there is a version of the Zapruder film with an additional frame between 312 and 313 - he calls it 312a.
What do you guys think ?

https://www.youtube.com/watch?v=UNWpLgInT7w

where did these frames originate, the source for this is?

Here's how that can happen. In analog video, interlaced video, 2 fields constitute 1 frame i.e., z-312. Extract both fields of that one frame (save as tif,png, jpeg, psd files), de-interlace those fields in Photoshop (which rids each field of odd/even scan lines) select field a or b, resize that individual field by 1-1.5% (whatever size works best for your need), shift left/right-up/down copy and paste to add to add the newly corrected field sized to the z-film frame sequence on display... and there you have 312a (now a frame).