For those with aftermarket headers / manifolds of a design that does not consider installation or removal with respect to the lower front arm and bracing (particularly on the convertibles), I did have success with the following:

1. Remove the single nut on the engine mount on the right-hand side of the car (exhaust side).
2. Jack the engine up enough to allow the exhaust to clear the bracing. I suggest that, if possible, just bring it up so that the stud from the engine mount is still within the channel created for it. This way there is no concern for muscling the engine back into place if it were to shift from this general location.

You *should* now have room to remove the header and clear the lower arm, studs, and bracing. On the verts, you may have to remove the additional bracing not found on the coups that spans the rear of the front lower arms.

I know there were some older threads questioning how to do this (with no solution from what I remember) but I was not able to locate them through search. Please feel free to link them here if you are familiar with these threads.