So I want to buy some seam sealer to seal some unsealed seams on the undercarriage to prevent dirt/salt/etc from getting into the seams to prevent rusting. I hear 3M makes some of the best seam sealers out there, but which one of 3M's sealers should I use?:

http://products3.3m.com/catalog/us/en001/.../

Also, where should I seal these seams? I mean, should I seal all seams that I find? I'm worried about sealing anything that might be a "drain" for moisture or water, or whatever. Can I spray Krylon zinc-rich primer & enamel over sealant?

Any thoughts appreciated.

 

Many seams have "drain" holes, openings, or gaps. You might be doing more harm than good if you don't really know exactly what you're doing. Only a Mustang design engineer could answer this question for certain.

 

The guy with the excellent taste in car colors is entirely correct. Seal up the wrong thing under there and you could trap water rather than letting it run off.