I have seen some elaborate and scary epoxy repairs that worked, but I don't think epoxy would be a good long-term option for this job.
To position everything for welding, a simple flat plat with a few holes drilled at the right places could serve as a fixture. Add some bolt and spacers, and maybe a couple of clamps, and that should work.
Be aware that serpentine belts cannot tolerate the misalignment that v-belts can, so make sure the pulleys are lined up with each other and not running at an angle to the belt.
The best option would be to find a bracket that does what you want. If not a production item, maybe something aftermarket. Hopefully someone here can put you on to a bracket that will do what you want.
To position everything for welding, a simple flat plat with a few holes drilled at the right places could serve as a fixture. Add some bolt and spacers, and maybe a couple of clamps, and that should work.
Be aware that serpentine belts cannot tolerate the misalignment that v-belts can, so make sure the pulleys are lined up with each other and not running at an angle to the belt.
The best option would be to find a bracket that does what you want. If not a production item, maybe something aftermarket. Hopefully someone here can put you on to a bracket that will do what you want.