Lore is that pre-1994 Campy taper was slightly larger (end dimension) than ISO, and they changed to ISO in 1994. That's why Phil Wood has recommended the JIS. They didn't make an old-Campy taper, probably because it's close enough to JIS. For a "chunkier" taper end, you'd want a slightly shorter spindle, theoretically, than the original Campy one. Campy road spindles changed at CPSC-time because the crank arm raised boss on the back side was changed. Here's a useful link at Bicycle Classics:
http://00eda5d.netsolhost.com/bottom.html