Slip joint question

[melter]

Hi I just did a 360/904 swap in my 73 A body I also swapped my 7 1/4 for an 8 3/4 in the rear. Now my driveshaft is to long. My question is if I put my slip joint into the trans as far as it can go, how far do I back it out to measure my center to center length for the U joints?

 

[mopar340dave]

These guys are some of the best in the industry.
http://www.dennysdriveshaft.com/how_to_measure.html

 

[pettybludart]

About 1 inch travel.