For the trunk floor seams...
For the trunk floor seams on The Paddock '69 Charger, Mike Paremsky used Wrth Brushable Seam Sealer, which comes in a can. Some other seam sealers are applied with a caulk gun, but they won't have the correct look for your Mopar.
If you've ever looked at any of the body or panel seams on your Mopar, you might think that the guys applying seam sealer at the factory were paid on a per-can basis. "Liberal" doesn't even begin to describe the application.
While installing new trunk floor extensions on The Paddock-sponsored '69 Charger ("Quarter Surgery, Part II," Mopar Muscle, April '99), Mike Paremsky, owner of Michael's Auto Body, where the work is being done, showed us how he applies seam sealer to inside panels such as trunk and interior floor pans. The original factory application was thick (over half an inch deep in many places), and not very even or neat. It also had brush strokes visible. After it was applied at the factory, it was painted over.
Mike prefers Wrth Brushable Seam Sealer for these interior areas. The Wrth seam sealer is the closest Mike has found to the original factory sealer. It brushes on, doesn't shrink as it dries, and is ready for paint in 24 hours. Wrth Brushable Seam Sealer is available at your local paint supply store.
 The factory application of...  The factory application of seam sealer was anything but neat and tidy. Mike liberally applies the Wrth seam sealer with a paint stick to all the joints and seams on the trunk floor, around the tail pan, and around the wheel housings. He primed the entire trunk floor first, then applied the sealer. The seam sealer was applied at the factory before the car was painted. |  After applying the seam sealer,...  After applying the seam sealer, Mike takes a brand new parts washer brush and drags it over the top of the seam sealer, applying the correct brush strokes originally found in the sealer after being applied at the factory. Though the factory didn't worry about "strings" and messy edges, if you want to clean up the joints a bit, lacquer thinner will remove the sealer from anywhere you don't want it. Allow the sealer to dry at least 24 hours before painting over it with body color. Other reasons Mike prefers the Wrth sealer over other brands are because paint adheres to it very well, and it doesn't bleed through the paint. |  Here's the finished seam after...  Here's the finished seam after painting, just like it came from the factory! |