The Subaru flat 4 engine range went through some changes in around 1999. Most of the changes were to do with internal details such as the cooling system, and whether certain models has SOHC or DOHC ‘heads, such as the 2.5 naturally aspirated. The main change which is of inserted from a VW conversion point of view is the fact that extra bolts were added to the bellhousing flange. Engines before the changes are known as ‘Phase I’, and those after as ‘Phase
The RJES bellhousings are designed based on the Phase II bellhousing flange. To use them on a Phase I engine, you simply don’t use the three extra bolt holes.
To make things more confusing, not all the Phase I / II changes cut in together. Some engines are crossover models with a mixture of Phase I and Phase II features, such as the 2.5 engine in the RJES Syncro