SPICER ... never seen 'em without grease fittings though. In applications that would munch GMB u-joints weekly, Spicer u-joints have held up without failure.
My 351W used to munch them all the time and my friend's F150 4X4 would too. Neither of us have had a Spicer u-joint fail after finally spending the extra $1.50 on them.
Remember not to over torque the u-bolts when tightening them too...over torqueing crushes the bearing caps and causes premature failure. I don't remember the specs, but it's surprisingly low.
i took them up to a local parts store and had them run the numbers for me. the numbers match up to a mustang II v-8 4 speed but the caps are very different than whats on the car.
the u-joints currently on the car have caps that are all the same height where as the ones that where given to me have two that are the same height and the opposite two are shorter by about half.
leads me to believe: shorter caps, less bearing, less reliable.
I second spicer, though right now I'm running a "performance" GMB at the trans, and a standard GMB at the rear to sort of act as a fuse. Gonna change to spicers this winter.