Are we discussing gasser tank installation or glow fuel, it looks like you mention a 6.0 engine.

With the gasser you can mount the tank/tanks anywhere you want, preferably on "CG". Gassers require "GAS" fuel tubing and tank stoppers...

The dual tank configuration will work fine, forget the tee'd idea as this is an accident looking to happen. Use the header tank plumbing concept. Essentially tank #1 draws from tank#2. This will work with no issues for either gas or glow.

If you need help with the plumbing schematic just ask.