Lee,
I owned one of those, and I'm pretty sure there were more than 45, although it was a small number. When I was waiting for mine to arrive, I called up Tom Jackson, who was making them, and he said he sold out of the 50 he had made in advance of his ad almost immediately, which shocked him, and he was scrambling to catch up because he had about 150 total orders. Also, it's not exactly a conversion kit. The frame was custom, like the boiler (which was, however, knocked off from the Trix B6, true). All the rest of it is, as you said, Rivarossi parts - drivers, pilot/trailing truck, and the tender, although I think the tender shell is cut down flatter on top. They weren't sold as any sort of "kit". Tom sold them as complete engines. He did all the modifications himself. Mine was a really smooth running engine. But alas, when I branched off from the PRR, I hacked and bashed mine into an SP&S atlantic.