Streetkas are not like normal Kas. Although they have areas that can corrode the floorpan and sills are bombproof. This is from the Ford workshop manual :
General design features
As, for functional reasons, a cabriolet body has a roof construction that is not integrated into the body structure, the floor pan and the A-pillars must be provided with additional reinforcements.
The A-pillars or the front roof frame have been reinforced primarily for reasons of passenger protection (vehicle rollover). Two rollover bars are firmly mounted to the bodywork behind the seats as a further passive safety feature.
The body has been reinforced in particular in the rocker panel area. The rocker panels in conjunction with the adjacent body assemblies form a reinforced box-type structure, preventing body weakness in the event of high stresses. These so-called composite connections provide a solid body pan structure. General body reinforcement areas
No high strength steel panels are used on the Streetka.
The high rigidity of the body is achieved by means of individual panel thicknesses of up to 2.5 mm and by special shaping of the statically important body panels and body components.
In the rocker panel area, this results in a total composite material thickness of up to 6 mm.
Panel layers and shaping in the rocker panel area Corrosion prevention measures Body components at risk of corrosion are zinc plated on both sides. PVC coating
A permanently elastic PVC coating is applied to areas of the floor pan at risk of corrosion, protecting these in particular against mechanical influences such as stone chipping
All the profiles of the floor pan as well as the cavities of pillars, rocker panels and frame side members are sealed with cavity wax Seam sealing and bonding
Joint areas of doors, hood and rear lid are adhesively bonded and sealed by means of clinched flange sealing.
Penetration of moisture is prevented thereby, significantly improving corrosion protection.
A critical corrosion area is the front subframe mounts just behind the wheel hubs. I caught the problem early and treated the rust before it got any worse.