71 Demon Driveshaft Length?

I am needing a driveshaft for my 71 Demon 340 / A833 / 8 3/4. When I look them up in my parts book I come up with 2 different lengths one is 48.96" 2 3/4" shaft the other is 51.96" 3" shaft. I haven't been able to find much info on manual trans length. Anybody out there mind pulling a measurement or happen to know the correct length? Thanks Warren