U Joint selection has me confused - 86 K10

[Orion88]

I'm swapping out axle assemblies on my 86 k10 (3.08 to 3.42) and I figured while I was at it I would replace all the U Joints on my truck. Problem is there are so many different part numbers out there for all the different applications that I no longer feel I can order them with confidence. I always use MOOG and I prefer greasable parts when they are available, but the more I look through Rockauto.com the more confused I get. Some are for the front axles, others are for the front driveshaft, others are for the front or rear driveshaft, some are this size, etc etc.

So do I even need to replace all my u joints? Truck has 101,000 miles on it and was very well maintained by the previous owner. She has seen a little time plowing snow since I've owned her but not much. I know the u joints on my front axle that I bought are worn, but I haven't checked the driveshafts yet. I know some people say you should always replace them when you replace axle assemblies, but 6 MOOG u joints would set me back a good $70 or more. So what is best practice and what are all the part numbers for my application??