I have a DL 5 litre Windsor, Fuel pumps makes a fair bit of noise and i have some 6 Cylinder pumps lying around ea - au,
Does anyone know if they are the same - or are the 8's different to the 6's ?

Yep, same unless the 6 cyl ones are from a CFI engine then no.
Unless you know these pumps are very good I wouldn't do it....it's such a pain to change them I wouldn't put anything but a brand new one in.