Do you sell heavy duty, non-greasable U-joints?

Yes!  We sell both Spicer and Neapco non-greasable u-joints.  Most popular is Neapco's Performance Dynamics u-joints.  These non-greasable u-joints are made especially for aluminum driveshafts.  Their oxidized caps don't rust and help the u-joints fit tighter in the yoke.