What is this (movie model of an) railway artillery piece? (As seen in "Return of the Living Dead")

Factual Questions
1

A couple of days late for Halloween, but I was wondering if any military equipment fanciers could help me identify an odd artillery piece—this model, as seen in the 1985 film “Return of the Living Dead”:

All I can say is it’s not the M65 “Atomic Annie” or the “Gustav Gun.” I’d be almost certain that the crew cabin and the radar/satellite dish parts on the left are later additions. I would not be surprised at all if the entire model is kitbashed from more than one source, and it’s entirely possible that the entire thing was scratch built, and not closely based on any real-world weapon.

But still, I wanted to check. Can anyone with a better eye or more experience in the subject enlighten me?

2

Possibly 14-inch M1920 railway gun - Wikipedia ?

A few more photos: https://weaponsandwarfare.com/2019/11/19/defense-of-panama-canal-batteries-and-accommodation/?noamp=mobile

The top part (turret?) doesn’t look quite the same though, and the crew cabin / radar isn’t there.

3

Actually, the (rather poor) picture reminds me not of an actual railway gun, but an M107 Self-Propelled Gun on a railway transport car.

Or kitbashed into a fake railway gun, because mediocre picture.

Note the arrangement of the elevating arms and the barrel length.