That link is to the faster-setting sealants.
Skygeek might have what you're looking for. They seem to have a wide selection.
Or you can do as I did; goop the tank up and assemble it with clecos and let it cure. When fully cured, rivet it.
I used Wirejock's idea for getting extra clamping force on the clecos, by using #4 nuts as spacers on the inside of the joint. Mine had those lockwashers attached so I put the lockwashers away from the airplane parts, which made them easier to grasp afterwards. They came off without any trouble.
The only downside was that my clecos wouldn't initially fit in my #4 nuts, so I drilled them out with a #40 bit in the drill press. Went pretty quickly and no problem. Still, I'm building an RV-3B, not one of the prepunched kits, so my view of what was no problem might not match everyone's.
Dave