Need help with HB diffs

[GorillaMaxx360]

2 questions for you guys.
1.) I have my car put together nicely except for the front diff the rear diff has 10,000 diff weight oil and i have a fairly heavy truck. Is ten k good for the rear of my heavy truck and what should i use in the front. I would prefer to keep the same diff fluid in the rear because i don't feel like refiling it again but if it will be worth it what diff oils should i use and will 10k work. What should i do
2.) i Have these diffs. i broke this

What part number or part name is this called and where and can i order/get it singly. Thanks guys