Best gutter/body seam sealant

Yesterday, while sitting in my F150 in heavy rain, I had water leaking out the seatbelt slots in my B pillars . Guess I have roof and gutter seams to seal!

(I guess would explain my cab corners rotting from the inside out)

Anyway, Here's some pics of what I have to work with:









What would be the best way to fix this without a massive ton of body work (stop the leaks)? Ideally something that won't shut me down for more than a couple days (as the truck show is coming up!). Window silicone? Flex Seal? Bubble Gum?  

i guess the standard answer is that it is not a quick and dirty fix unless you want to re-do it soon after. wire wheel to remove all seam sealer and treat the rust. let dry and brush lightly again. then use fast and firm by 3m and allow to thoroughly dry before paint. if a repaint is in the near future, then you could try masking it off very closely and using brush-able seam sealer but only where you see gaps. either way, clean as much as you can.

Wasn't planning on a full repaint as IMHO that's a body work rabbit hole that'll bankrupt me (lots of dents, lots of surface rust, and most of the aluminum trim is bashed up) and likely render the truck too "nice" to drive (which is useless to me). This truck is a daily driver (that can be used to haul things and drive long distance), not a show queen.

Would Chassis Saver work here? I still have most of a can leftover from painting my bed before dropping in a plastic bedliner (yes, I did put something in the lid!).

Thanks Mat. Nice to look at this in two ways and what options are there for each: true, longterm fix or just extending the life a little more.

Curious why only in the gaps?
Thoughts on the 3M All Around Sealant over the top of what is there after removing lose pieces?

mat in tn wrote

i guess the standard answer is that it is not a quick and dirty fix unless you want to re-do it soon after. wire wheel to remove all seam sealer and treat the rust. let dry and brush lightly again. then use fast and firm by 3m and allow to thoroughly dry before paint. if a repaint is in the near future, then you could try masking it off very closely and using brush-able seam sealer but only where you see gaps. either way, clean as much as you can.

3M makes a Drip Check sealer just for this in a tooth paste tube and I used it on my truck.
Yes use wire wheel and treat the rust before adding the sealer
https://www.3m.com/3M/en_US/p/d/b40067210/
This is not the same as seam sealer used when sealing fire wall to cowl or floor pans.
Dave ----

this product looks great. im curious how much different it would really be from the brushable seam sealer.