The 1978 and 1983 Workshop Manuals for the Perkins 4-99, 4-107, and 4-108
are different.  The 1978 manual shows the 4-108 configuration better.  The 
1983 manual may use the 4-99 as an example.  There was also a later version 
published around 1991 that was identical to the 1978 version but had a photo-
graph of the "New" 4-108 - the last model made with a Bowman heat ex-
changer.