/6 to V8 swap

The 8 3/4 axle is about 2" longer than the 7 1/4 axle, the driveshaft will have to be shortened.

Also, FYI, a 727 is also about 2" longer than a 904 and will need the driveshaft to be shortened also. (In case you consider it for the future).

You may want to consider the 1" torsion bars from Just Suspension or the 1.030" torsion bars from PST if you want better handling. Many guys who have swapped to these are happy with them and they are not too stiff.