7 1/4 to 8 3/4

So car came with a 7 1/4 and I put in a 8 3/4 got new shock plates for a 8 3/4. The best I can tell is with a 727 trans I need a 44.99” driveshaft. 48” is to long. Am I correct? Measurements are not including yokes
That is for a 72 Duster/Demon with a 340 according to the chart I'm looking at...