Cruise friendly low 12's with a 340 Dart

Well, I personally dont think those goals can come together. Honestly, the best bet to get milage, and torque, and drivability, is a 4" stroke. A medium duty cam, and ported iron will do it. The last one cost about $4800 re-using what you can. Maybe sell the rest of the un-usable parts for some cash reserve. That's what I'd do. No way to get 16mpg, low 12s, and drivable out of a 340. It simply can't get the job done.