http://www.northerndrivetrain.com/
The best information, a true innovator and everything is always in stock! Seriosuly - largest Spicer dealer in the Midwest.
Here is the joint you want - life series so you never need to worry about water intrusion or greasing the joint.
http://www.northerndrivetrain.com/product/SPI-5-1350X.html
I switched to nothing but Spicer life series joints and have yet to have a failure in 5+ years due to lack of lubrication or water intrusion. With one of these in your hand you will know what I mean by the seals are ridiculously strong - I needed a channel locks to get the caps off my 1410 stuff as they lock in so well.