What is the deal with a SAS on an autotrac truck? Most things I've read say you have to swap it out due to the front driveshaft spinning all the time. I've got a '99 z71 that is begging to be bigger then my 4runner. Whats the real deal?

Somebody correct me if I'm wrong, but I believe the autotrac feature is solely controlled within the transfercase, so what front axle is in the truck is a non-issue.

In any case, the autotrac cases also have a regular 2wd mode so I don't see where there is an issue. Unlock the hubs, shift it into 2wd, and go.

autotrac uses clutchs to engage frt diff.these spin all the time to prevent heat build up in clutchs. the clutch pac has slight preload that allows slippage when not applied but when in 2wd everything still have to spin otherwise clutch life and fluid life would be very short
with sas if you left frt hubs engaged all the time it probably would work as long as frt drive shaft angle is not to much
your best bet is to swap a no auto trac case into truck