The heaters tubes have to be removed and replaced with steel tubes or left off untill after the dipping process. Acid dipping has the advantage that it gets into all the sill sections and box sections that media blasting carnt. It can then be followed up by e-coating wich is an electrostatic dipp painting process that is the industry standard for most of not all new body shells and chassy components. This coating again gets inside all the box sections that ordinary paint carnt. The combination of the two cures any rust you carnt see and could never get to with a blaster and then encapsulates it preventing future corrosion.
Heres a pic of a 911 thats been through this process.
Steve