Ford racing C springs is a good deal for a good spring, they are just a linear rate spring and some want more of a drop.
If it was me I personally would go H&R race (or H&R sport for a lower drop), Eibach, or Ford C springs. The H&R will be more performance oriented and are progressive rate vs linear (progressive = tighter coils as they go to the bottom so the more you push the harder it pushes back this lets you have a higher spring rate (max) and a better ride) while not pushing it hard)
I had C springs and they are fine but the drop was not quite enough... they can be cut though to give you the right drop
you cant cut a progressive spring usually.
Also... if you was to get say a spring that lowered you a touch to much you can just buy a set of urethane isolators and it will lift it back up, you can put just the top or bottom in and even it out how you wish~