1951 Flathead to C4 drive shaft advice

[pistonbroke]

Put the yoke in the C4, push it all the way in. Now pull it back 3/4", then with help messure from the center of the U joint cap in the C4 yoke to the center of the U joint cap on the rear end. This is the messurement needed and it should be done with the vehicle sitting in its normal stance. Tim