Until someone writes a page about the Morgan 4/4 in general, you can find a short history of the car at Morgan 4/4 Wiki.
The first 4/4, the Series II, was introduced in October 1955 and used a side valve 1172 cc Ford 100E engine with a Ford 3-speed gearbox.
In October 1960 the Series III 4/4 was introduced; this used the Ford 105E engine with a Ford 4-speed gearbox.
In October 1961 the Series IV 4/4 was introduced; this used the Ford 109E engine with a Ford 4-speed gearbox.
In February 1963 the Series V 4/4 was introduced; this used the Ford 116E engine with a Ford 4-speed gearbox.
Later 4/4's used the following engines:
From February 1968 1599 cc Ford Kent Crossflow.
From November 1981 1588 cc Fiat twin-cam.
From March 1982 1597 cc Ford CVH.
From November 1991 1597 cc Ford CVH EFI.
From April 1983 1796 cc Ford Zetec.
From 2006 1798 cc Ford Duratec.
From 2008 1595 cc Ford Sigma
From 2008 Sport