According to my Ford Parts Interchange Manual the dimensions on a drive shaft used on a '70 Cougar with an FMX and a 351C-2V (if that is what you are using)is 53-9/16" x 3" and the yoke is 8-7/32" x 3-1/2". If the FMX is used on a '70 Cougar with a 351W (if that is what you are using) the dimensions for the drive shaft is 53-9/32" x 3" & the yoke is 8-7/32" x 3-1/2" also. John