best bang for the buck?

chassis and suspension are not my issue. in a five mile radius of my shop i have S&W, ED QUAY AND PERSSISION CHASSIS, chassis questions will be directed at them.
what motor 360 or 440 will take me the furthest.
at the shakedown at e-town this last summer i saw a small block ford mustang with a big turbo go 7.77 in 1/4 mile and he drives it to car shows when its not racin.
the after market parts and tech for a turbo mopar are not avaliable like a mustang.
do i wana go 7s? not right now.
i want to learn how to get there, and want to do it in a 68 dart, mopar powerd.
i have 2 440s so im gona go that way, and figure it out myself, thanks for the help.