Different drive shaft?

Snake said
69 dart with 7 1/4 going to the 8 3/4.I have read that if I install an 8 3/4 I will have to chandge my drive shaft.says axel centerline to yoke centerline is greater. on the 8 3/4 than the 7 1/4 I know I need dirrerent shock plates and thought my drive shaft would have to shortened thats it.Any thouights.
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As long as you're not changing the position of the tranny, I'm pretty sure your drive shaft will have to be shortened because the 8 3/4 pumpkin is longer (pinion yoke centerline to drive axle centerline) than the front end of the 7 1/4 and 8 1/4.