The lack of kickdown linkage availability when it was built is why I suspect it has a manual valve body.
A previous owner built the car years ago.

Installing kick-down linkage was suggested to her right after he passed, but I think she simply doesn't feel comfortable driving the car.
She was always the passenger in it with no aspirations of driving it.

Like I said before, her opinion is that you shouldn't have to shift an automatic other than put it in drive.

Different people in the group have offered to do the work to make it more drive able (to her specs) but it seems that isn't what she wants to do.

I think she's afraid of the power that the car has.
It's more than anything that she's used to driving.