I think it's a matter of opinion and just trial and error as to what suits you.
I did my diffs and put 300K in the front and 100K in the back. You read right.
I wasn't sure about the weights either. Was going with 30K and 10K to start with, looked too thin.
Sounds too heavy, but I'm glad I did it now. I just bash. Do a lot of hill-climbing. It's a real turn-on for me to be easing it up a hill and all 4 tires are spinning. Here is a link to how one guy has his Mammoth set up. He is using 300K in front and back.
http://globalservices.globalhobby.com/globalforum/viewtopic.php?p=39292#39292 I know it's not a Savage. Just found the link, read a lot of his posts and he makes sense on what I've read.
Point being:
Go ahead and do the 4 spider mod. (you are doing that?)
Put what ya have in the diffs. If ya don't like it, change it. There are quite a few winter days coming up where ya are going to be working on it.
Get it together and see how ya like the setup.
Whatever you do,
don't fill them up too much! I did my X-term, I made that mistake. Got one that is leaking. Leave enough room for the oil to expand or they will leak. Good luck.