Seems a lot easier to just plumb a solenoid line into the intake manifold and start it on propane (like those small Coleman propane canisters)
Heating the entirety of your fuel tank takes a LOT of energy. Heating the intake manifold is more practical, but you're still likely plugging something into the wall.
I think plumbing in a little Coleman bottle is the ultimate solution. There's solenoids available for RVs and such, and all you'd really need is some line, a fitting, one of those solenoids and a normally closed momentary relay on the 12v acc. That opens for some adjustable amount of time when it gets power.
Anyway, I live in CA, so it's not a big deal, but that was what I would try if I lived somewhere that gets lower than the ~25F it sometimes gets around where I live. I quickly came to the realization that heating anything would take a crap-ton of energy and was only practical via extension cord.