d30? how strong do you think it is?

[Jeffy]

my point was running the straight axle to eliminate the vacuum disconnect.  So I can use any xj or tj axle for that?

Yes, that will worn BUT your front driveshaft will not turn 24/7.  YJ driveshafts aren't balanced so you might get some vibrations at higher speeds.  Also, some people add seals to the axle housing to keep them from leaking.  I'm not really sure if this is necessary since mine don't leak.

[YJmechanic]

add seals where?  You mean out at the end of the tube as well as the inner seal?

[BlackYJ]

With the vacuum disconnect axle there is a seal just past the actuator towards the knuckle.  When you convert to a one piece axle you should add a seal inside the pumpkin to prevent lose of oil.  The driver's side has this seal.

I have driven my Jeep at highway speeds in 4x4 with no problems