The way to work it out is for every ounce of lead you are casting you need 10lb of nylon plus 10lb for safety
So a 5oz lead would need a MIMIMUM of 60lb nylon for the rig body
If you are power casting it is advisable to use 80lb nylon.
I use 60lb Greased Weasel for my rig bodies as I never use more than 5oz of lead
A 3 turn grinner is what Id use as the main knot for snoods and hooks then go to a 4 turn grinner on the rig main body. It can be tricky tightening the knot so use Adas tip to avoid a hook in the finger. For the lead link, I tie the knot and then attach a plain lead to the link to give some grip on tightening