Dana/Spicer application guide - Fill in blanks for K5 Blazer
The Expert - K350 - Information for driveshafts, u-joints, axles, heavy axles, light axles, Driveline
There's actually 7 u-joints total - double cardan in front driveshaft counts as two 1310's.
http://www2.dana.com/pdf/J321-CV.pdf