The hyd cams are much more streetable and need little maintenence. Solid lifter cams need regular adjustment and performance can vary with changes in ambient air temp and barametric pressure. If your FE originally had a hyd cam, it would be wise to stay with a hyd model because the
oil passages are already there. I chose a Comp Cams 270H model for my 428, which is somewhat conservative, but you can choose from several different manufacturers and grinds. Consult your engine builder as to the type of driving you will do with your Cobra. Good luck.