Rick, thank you for your last message via eBay, I hope you don't mind me moving our discussion to an open forum, but I'm hoping that some of the other guys on here will be able to clear up any concerns I have!
As you said, you have a current (red) logbook, which is good, but what concerns me is that there is no mention at all on the logbook of the kit makers name or model assigned to it, or even any mention that it is a kit car.
I would expect there to be at least something in the notes section on the cover of the logbook, saying that it was registered as a kit car or modified on ... date.
You said the logbook states the model as a 'Panda 4x4 Pickup'. To the best of my knowledge Fiat never produced a pickup under the Panda model (that would be the Fiorino). So, I 'assume' that when the Panda was rebuilt as a kit car, rather than register it as such, they just informed the DVLA that it had been altered to a pickup.
Converting/altering a car to a pickup would not be the same as completely stripping a donor car down, and using the parts to build up a kit car.
So, based purely on the information that you've given, it does look as if the kit car has NOT been registered as a kit car, as there is no evidence in the paperwork to that effect.
That would mean that to register it now, it would need the SVA or whatever test.
As far as the numberplates go, I don't know the full in's and out's of this particular kit, but even if it did retain enough points to get by without a Q plate when you bought it, it won't any more, as you changed the engine (and I assume the gearbox as well).
So, the only parts left that would count as original (if they are original) would be the 'axles' and the suspension.
Chassis/body, and engine carry the most points, and both are gone!
In addition, you've not even declared the new engine number yet. What happens if the DVLA want an inspection? They are going to turn up and say that the vehicle doesn't match the paperwork, and refuse the change. So that's massive issues even before you've got to the SVA stage!
When I saw the car come up on eBay, I started frantically searching the net for any info I could find, as this car ticks almost all the boxes for me.
I came across you're posts on here, and have read through pretty much every one of your past posts relating to this vehicle. I am genuinely interested in buying, but from what you've said so far I can't see a way of getting this back on the road legally. Is that why you haven't managed it in all the years of ownership?