If you want a regular cab you are almost certainly going to have to go with the older body style (94-97). There are regular cab Superduty's but they are only available in long beds, and since the proliferation of the larger cabs the reg cab SD's are almost non-existent..... and since they are almost entirely fleet trucks they mostly have the 5.4l gas hog.

Of the remaining choices, a 96 or 97 would best suite your needs. Engine mileage is almost a non issues if it has been properly maintained, but you will obviously want the lowest mileage possible. The auto tranny will be the weak link if it's over 200K miles. The manuals are nearly bulletproof in a stock or mildly modified truck, and clutches are easy....so that's how I would go.