Looks like the rear end of a car to me.
I think you're right. I missed that black blob at the bottom (the wheel).
I'd been listening to Sherry Fiester interviews about where she believed a
frontal shot originated from. From the area behind whereabouts the truck was at the time of the assassination.
If the shooter was on the south side, the truck was seconds away from blocking the LOS. Or even blocking the LOS, from that angle. The truck appears to be crawling along from z-404
Or, what if a shooter fired from the back of the truck out through a hole in the side.
But would anyone even contemplate a headshot from the south side ... and potentially hitting bystanders behind the LOS.
It's hard to imagine anyone would have taken that risk firing from the south side. Firing back up Elm towards crowds.
I've not found an interview where she discusses the truck, but it's a potential spanner in the works for her theory.
?\_(ツ)_/?