The taper problem turned out to be a substantial twist in the 36” bed on my
old Atlas lathe. The cabinet/bench was not stout enough to resist any attempt
At counter twisting with shims,so I made up a stout top from “c” channel
Notched and welded it in place. Leveled it in, and the twist came right out.

Just something to check if your lathe is turning an unwanted taper.