nice work!!
Yep, nice job. I'm curious what the riveting tool looks like.
On the Custom's channels, the vent window back seal is riveted to the channel as well. The seal kit comes with the rivets. I got my channels and vent window seal from Classic Auto Parts on okc, and I'm pretty sure they were the manufacturer (Dale's Manufacturing..........same owner), so my guess is the rivets could have been sourced from them. They can be set without a special rivet tool, I've got a post on those somewhere.
I'm guessing the channel you're showing must be the door latch side though, not the vent window side.
Basically, I clamped a 1/4 x 2 steel bar in a drill press vise to set the channel over and used a transfer punch in the drill press to set the rivets.
This is the tool I used:
https://www.ebay.com/itm/232639089602?rmvSB=true
I also installed a new vent window back seal and used this tool on those rivets too. Those rivets are smaller, but were tougher to set. After setting, I used a 1/4" socket extension to flatten them a little more.
That tool is very close to what you get if you use a transfer punch. I just picked an odd size punch out of my set that wasn't likely to get used and ground some of the point off. The tips on a transfer punch are a little too long for those tiny vent window rivets. Thanks for sharing that, I had no idea a regular tool was available.
Or you can be lazy like me and send the whole works to Jeff at Restoration Specialties. He's really good at it.