Drip rail Seam sealer?
 

What is the preferred seam sealer for the drip rail on my 68 truck?

Re: Drip rail Seam sealer?
 

I've used both 3M and SEM self leveling seam sealers, been pleased with both.

Re: Drip rail Seam sealer?
 

Just did this myself.
Agree with the earlier posting...brand name - 3M or SEM. 2K is latest and greatest, but I think modern 1K from good mfg. will still be better than original. Overall it's an inexpensive project and the price difference from low end to high end it small.
I'd suggest self leveling unless you have long arms and/or are comfortable "messing" with caulk. Accessing the drip rail is a bit awkward.
Self leveling, it's really just that - it does most of the work. You run the bead and wait for it to settle/level out. It does start to harden pretty fast - just a few minutes or so, so you need to be quick with the smoothing out the ends. For the bulk of your bead or seam you really shouldn't have to mess with it. Whatever you use though, you might consider running a line of tape along the interior side (roof side) to establish that border. After it's about 1/2 dried you can peel it up. If you run a nice bead this may not be necessary.
IMPORTANT - Do it where your truck is level.

I used SEM 39777 which is a 2K high build self leveling sealer which runs a bit slower/thicker and the supply store lent me (no charge) the expensive 2 piston caulk gun.