[Mg-t] rocker shaft?

[Carr&Edwards]

We have a puzzle before us:

We're in the process of a full rebuild on my TD engine (XPAG/TD2/22791, which
had an early, banana-holes head installed by a DPO), using a (correct)
round-holes head from an even later XPAG.  The replacement head needs a new
rocker shaft.  The rocker shaft that was on the replacement head measures 14"
-- but according to the Moss catalog, the later engines take a 14-7/8" shaft.

Did some DPO install an incorrect shaft in the replacement head, or is the
Moss catalog wrong?

Help!
Sarah Carr
TD3942EXLU in PA