Cruise friendly low 12's with a 340 Dart

can't beat a six pack for gas milage, also run an adjustable vacuum advance. i'd build atleast a 360, around 10.5-11:1 with aluminum heads (so you can get away with pump gas). make sure your piston/head setup will have good quench. probably a comp tight lash street roller (comp). that'll get you close, i'd probably build up a 518 w/ OD so you can run a 4:10 gear, that way you can still cruise. thats probably how i would go about it.