fyi- unlike powder-coating or traditional automotive spray-applied paints, it's VERY hard to get someone to do a small e-coat job (like one car) due to the potential for e-coat tank contamination.
Contamination is not an issue nor is it their concern. The issue e-coaters have is the disruption of the line to do old parts. The process has about 17 steps of various acid washes, rinses, etc.. The lines are geared and timed for production cleaning and coating of new stampings. They know that a new stamping will take x amount of time in a specific bath and the lines move smoothly. However, its anyone's guess how long it would take to strip and clean a 40 year old painted and rusted part - subsequently holding up normal production. THAT is why its hard to get someone to do a small job. But there are companies out there who specialize in the small jobs and will take on stripping and coating old metal. Make no mistake, it ain't cheap !!!
