I'm not familiar enough with the TR6 pump to answer that question, Don. The TR3 pump uses 'reverse' compression fittings (nuts have male threads), so definitely not tapered pipe threads. But I'd have to go measure a nut, to tell you the thread size/pitch.
Unfortunately, they also used a special ferrule (compression sleeve); modern sleeves don't fit quite right and frequently leak. Someone put up a web site showing how to 'siamese' two ferrules, but I wound up making a replacement nut anyway that was enough longer to seal with a modern ferrule.
I have seen people jam tapered pipe fittings in, though, and get away with it. The metal of the pump body is fairly soft, so I would guess the threads are deforming to match the fitting. Haven't tried that myself, though.