Why not just measure and send to driveshaft shop to be made longer or shorter

Can you name a few drive shaft shops that will do this? If so, please share with the forum. I bet there would be plenty of people willing to pack up their drive shafts and provide specs of what they are seeking, including the balance.

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Past mb: '73 450sl, '81 280slc stick, '71 250, '72 250c, '70 250c, '79 280sl, '73 450sl, parted: '75 240d stick, '69 280s, '73 450slc, '72 450sl,