drive shaft length question

[RJK3]

I've gone from a /6 904 to a 360/727, 8¼ rear end. Super stock springs.
I seen that the difference in lengths of the 2 trannys is 4".... I've installed the 727 slip yoke to the drive shaft, placed it on the output shaft bottomed out, pulled it back ¾"-1" and checked the distance at the rear...I get 3".
The car is a 73 Duster.
Should I remove 3" as measured? Or the 4"?
Thanks for the help!

 

[Bad Sport]

My suggestion to you is to contact the shop that you want to use to shorten and balance it and ask them how they want you to measure it. Shops sometimes differ in the way they ask you to measure.

Keep in mind when measuring you want the rear suspension loaded, as in jack stands under the diff, and then take your measurements.

Just my two pennies.

 

[RJK3]

Will do. Thanks.