Paul Vreede shed light on the Probe Force One origin -
Seeing the Probe Force 1 kit once again provoked a feeling I'd seen something like it before. Still can't put my finger on where exactly, but one of the American SST designs is what I thought. A google revealed that what I had in mind was the Boeing 2707-300 design, which has that distinctive tail and the four engines in a delta wing.
I then discovered that apparently it was NASA that did a lot of the initial work, using a design called SCAT-15F (Supersonic Commercial Air Transport) which they continued to test until the early 80s. That had a much longer wing (though a smaller tail) again with the four engines in round housings.
As you can see from the pictures, it's very likely that some depiction of these craft will have inspired the looks of Probe Force 1. If you do a google on "scat 15f" (between quotes to get the exact expression) then there's a lot to read about it. And Dark Roasted Blend has a nice collection of SST pictures.