Driveshaft...

Long ago my driveshaft was shortend due to replacing the 904 with a A500 & about a year back I started to feel vibrations... So I went at the pinion angle & gearbox angle, changed tires & so on... But now I'm pretty sure the inner pipe has come lose inside.
:(
My question is: does anyone know if there's a one-pipe shaft that's 50,5 inches between the center holes of the u-joints? (to fit between a 8,1/4 axel & a A500 trans)