3 days, while not impossible (nothing is impossible), is highly unlikely. You have exhaust issues, wiring issues, driveshaft fabrication, PCM reprogramming, fuel system upgrade, etc, etc. Putting the drivetrain in the car is quick and easy, it is all the ancillary stuff that takes a bunch of time. If you had someone helping you that had done the swap already, you may be able to do it in a week or two.