Re: EF/EL Fairmont Ghia
If you get headers fitted, make sure the primaries are the small ones, such as the 38mm (i think) for the Pacemakers, or get Wilcats or similar. Also have the zorst fitted with a 2" pipe from the muffler back. If not, and you decide to use the 41mm style primaries, have a restrictor fitted inside the cat.
The reason for all this is that if you don't do this, and simply fit a 21/2" all thro', you will lose all your lowdown torque and "driveability". It will be great from about 2500 onwards, but who drives around at those revs all the time?