OK, here's the driveshaft issue.
If you do extended arms with the stock driveshaft, yes it pulls the shaft out a bit.
The key here is that it pulls it out far enough to leave LESS than MINIMUM SPEC of driveshaft engagement into the tranny tailshaft. Put another way, the "stock" engagement into the tranny tailshaft leaves less than 3/4" of extra before you are below spec. This is why Hotchkis only went 1/2" back on their extended arms....keeps the driveshaft engagement within spec.
This lack of spline engagement, in turn, leads to premature wear on the tranny tailshaft bushing due to higher side loads.
There is also the increased (albeit still small) likelyhood of twisting either the yoke or the output shaft splines due to this reduced engagement. Something to consider if you're not just "cruisin" in the car.
Personally, if I were to goto 3/4" extended arms (I'm not, but that's been covered before in other threads [img]smile.gif[/img] ) I'd consider the driveshaft to be mandatory.