Streetable 12 second 20+ mpg slant six?

20 mpg in town or the highway ??
I've had dozen of /6 cars I wouldn't brag about any of there mileage my 318 5 Ave gets about the same. If you don't think you could get 20 with a mild 360 then start with a 273 still miles ahead with power potential over a /6. 273 is only 50 cid bigger but it has 8 intake ports vs 6 and the 273 flow stock what a fully ported 6 would plus you can add a overdrive easy.

The problem I see with a turbo six is 90% of the time your driving a stock powered slant six around.
I'd rather have a car that got slightly less mileage and was a blast to drive 100% of the time.

My 5.9 jeep gets 13 mpg in town and about 20 on the highway. If you installed that in my cuda both of those numbers would go up.