Help with an 8 3/4 swap

From everything I've read you would need to shorten it 2-1/4" because that's how much more the 8-3/4 pinion yoke sticks out, but not all information on the net is accurate so you should measure. You do that by having the car setting on all 4 wheels and slide the slip yoke into the trans. and pull it back out 3/4"~1" and measure from the center of the U-joint cap on the slip yoke to the center of the u-joint cap on the rear end yoke. That's how long the driveshaft needs to be center to center.