It can be done with the Intake on.. But My money says pull it.. You'll need PCV Hoses, Fuel Lines and NEW Clamps.. And do the Water Line Deletes that go from the Back of the Motor to the T-Bodies.. They can be difficult and NOT NEEDED.. but keep the water that goes to the Turbos..
Electric Battery Impact Screw Driver with an Extended Phillips Bit works to get the Screws out..