Filling seams

[hotrod ford]

I'm on the last leg of body work for my truck. Body is pretty much as straight as I can get it so I'm starting the seams. I bought this stuff from 3M called Plastic Metal. It is not working as I thought it would. I'm trying to make the hood look like one peice with no seal but it is being a pain. Has anyone ever done this or am I just waisting time and just fill the seam and be done with it? If so, how did yo do it?

[72BahamaBlue]

After I derusted and primed mine, I used some white 3M Marine caulk along that hood seam. Carfully wiped away excess with thinner, looks like stock. I ended up not using that hood...yet. So far, sitting 3 years outside in rainy NW weather, looks like it was done yesterday. That caulk is really stringy and pricey, but very strong and holds up very well. I just might use it in the bed seam too.
I've also tested DAP butyl rubber flashing and gutter caulk, also from Home Depot. That also seems to work well.