It's cheaper, $52.95 with free shipping (free shipping to Canada too), very good and detailed instructions(color pictures, step-by-step, etc). Also, shipping is fast, to Canada only took a couple of days. If you have any problems or question, there a phone number to call and he'll help you out right away.
I'm not sure about the Autometer unit, but the Pony Express Adapter will install in behind the passenger kick panel near the computer. Try installing the Ford tach driver there and you'd get a check engine light!