Upgrade to Rev.4 from older versions of Sparrow LITE board

The main difference between Rev.4 and older versions of Sparrow LITE boards is in another 3 signals added to the internal system connector ZX_AUX50 - /NMI, /M1 and /RESET.

ZX_AUX50 connector schematics

So in fact you can upgrade the Sparrow LITE Prototype 2, Prototype 3 or Rev.3 to Rev.4 by soldering three wires to board, as you see on photos:
upgrade to Rev.4 - whole board photo
upgrade to Rev.4 - detail