So I take my 70 duster and drop the 7 1/4 rearend and put in a 8 1/4 out of a 74 dart. I go to put the driveshaft in, and remembered that the 8 1/4 is larger, so I know it won't fit. I drop the car back down put it in the back of the garage and start hunting for a driveshaft for a 904 trans and...