All tapered square spindles have 2-degrees taper, and all Superbe/Sprint spindle tapers were "superbe" (Campy, ISO) sized (about 0.2mm smaller between opposite flats than JIS tapers).
It's the odd 108mm length of the "later" (~1980's) Superbe and Sprint spindles, in Campy ISO taper size (same 2-degree taper angle as JIS) that makes these spindles unique and, as a long-obsolete wear part, hard to find.
FWIW, an "effective length equivalent", spindle in JIS taper would be 103mm, the same as 7410-series (~1994-1995) Dura-ace. Perhaps NR Pista would be close?
David "usually just uses whatever minimally clears the chainstay" Snyder Auburn, CA usa
> In a message dated 10/7/07 5:24:07 PM, mitch.harris@gmail.com writes:
>
>> <<But what about taper? I thought that was the reason Grant and Riv.
>> recommended a specific Phil BB for the Superbe.>>
Chuck Brooks replied:
> "Modern" BB spindles have a 2 degree taper, +/- seconds of a degree. It
> is
> not that critical, and seems to be one of those "over-hyped" "technical"
> points which many folks agonize over. I think Grant made it out to be a
> much
> bigger deal than it is. I like Grant, but he does write good copy.
>
> The length of the spindle's tapered section and its cross sectional
> thickness
> is much more important than its taper.