drive line

the 65 barracuda now has a 727 and has 8.75 in it. I put the yoke in transmission all the way back it out around an inch, there is weight is on suspension and I took measurement from center to center and got a measurement of 46 inches, does this sound like the right process to get length of driveshaft? side note is there a shorter transmission mount out there i used the 65 rubber mount and the tail shaft hits the bump stop in the tunnel.
you could shove the yoke all the way in , mwasre ,then tell the builder the measurement and how you did it , if he`s any good , he`ll know what to do/cut it 1'' shorter .
always was told by the shaft builder to do that way ...