Look at the current technology in Sprint cars. There are many advantages to minimzing the distance from where fuel enters the intake airstream and the cylinder.
The latest hot setup (mechanical injection, but the following points still apply) is called "down nozzles" which require a special cylinder head that allows the injector boss to be machined into the exhaust side of the head, placing the injector discharge immediately above the valve seat on the back wall of the intake port. Getting the fuel away from being above the throttle blades stops the icing problem, and minimizing contact time with the inlet air drastically reduces water condensation problems as well as freeing more of the inlet system to carry only air instead of being crammed full of fuel vapor. Even with your proposed slant 6, 90% of the fuel won't vaporize until it gets into the cylinder.
It will if I get it's temperature up enough before it enters the carburetor (or fuel injectors). It all boils down (no pun intended) to how much energy you put INTO the fuel to overcome that "latent heat of vaporization" problem. Heck, you could actually inject ALL the fuel as vapor with enough fuel preheat--although depending on how the preheat was done (electrical or exhaust gas heat), you might have to do the "startup/warmup" portion of the drive on an alternate fuel--and you'd have to be careful not to "overheat" the fuel to the point that carbonization became a problem.