had similar issues when i rebuilt a 2003 st which had tin worms issues in the rear wheel boxes due to fords lack of sealing and the awful polyester arch protectors which hold damp and salt in that area.. i rebuilt all the susp F&r with new parts everything was seized solid , i happened on a basic KW kit from Germany, and as this is a track day and a occasional driver i needed decent road clearance but good handling and despised the front down look that Ford had left in the design.. i removed everything rear seat wise and lightened car without anything that would fail an MOT.. battery is now in rear pass footwell, and engine bay is clear of all trunking with a cold air feed from filter at the left lower valence area..I used KYB struts with std springs front and the kw rear springs and shocks with the adjuster part at the top bolted in through the rear x member. and set to the lowest it can be, arch is approx 20mm over the tyre rear, and 30 at front.. all 4 wheel aligned and set it handles amazingly wee bit hard at the back but i plan to lower the rear spring rates as even st std rears are too stiff for fast work on bumpy Irish back roads..