The E3 exhaust manifold is found on all Svo, Turbo Coupes, and Merkurs produced before 1986. It can be identified two ways. 1- is by the casting number is will read as followed E3*** ***** ** 2- is by the opening to the turbo it is a smaller peanut looking shape. As Seen Below
Notice the crack to the right of the opening. This is a common occurances with these manifolds and a major reason why most upgrade to the nore durable E6.
Post 1986 Ford switch there production to what is refered to as the E6 manifold. Like the E3 it got its name from the casting number as well E6** ***** ***. This turbo can be ported to some adaquite efficiencey.
The E6 , as you can see has a considerable difference in the opening to the turbo compared to the E3. It is also less pron to cracking, although it does happen.
There is another alternative to the E3 or E6 manifold. That is the ATR Header. Some love it Some hate it. The price tag of $495 has kept me away for now so i cannot give any personal testamony on its behalf.