Richard,
Although I've seen a few, I've never owned a Logan. So I'm not particularly familiar with accessory availability. However, I expect as Chuck implied that taper attachments are scarce. There are a lot more Atlas lathes around than Logans and the taper attachment is probably second only to the tool post grinder in its rarity. However, two things - first, on the Logans, the cross slide has to be changed out in order to use the factory taper attachment. and second, looking at the drawings, the two pieces that you found are likely the most difficult to make from scratch. We happen to have drawings made of the Atlas taper attachment. And from the catalog photograph of the Logan unit, I see no reason why the Atlas one wouldn't fit the Logan lathe. The only two things that you would have to do are probably minor height adjustments to the slide. And adapt the bar that sits on top of the slide and attaches to and drives the cross slide in or out to the standard Logan cross slide. On the Atlas, the push-pull bar attaches to the cross slide in the hole where the screw attaching the cross slide nut normally goes plus the tapped hole for the screw that normally attaches the cross feed screw cover or guard. Anyway, take a look. The drawings are in the Atlas-Craftsman section of Downloads.