About the only thing I have pinned own with any degree of certainty is powertrain.
I would LOVE to build a moderate Ford 460 for the cheap and easy displacement.
Live axle for simplicity.
What I would use for a transmission is a good question, I would prefer a wide ratio spread for creeping around at parking lot speeds and leaving the clutch out, while having plenty of top end gear for keeping rpm's down on the highway at eye-watering speeds.
Oh, and fuel economy of course!!!