1st question: Have you broken a birfield yet? If not, then just carry a spare.
For strength: 30 spine longs (hubs will break first), then Marlin 06's, then birf eliminator.
If you have not broken birfs, and don't drive like lead foot larry, then don't worry about any.
Just keep the front axle open and your tire size below 36" and you'll be fine.