there's a ton of different combos. I dont know them all. I think people do 30/8.8 44/8.8 44/44 44/9 9/9 60/60 or 60/14. I'd try for 44/9 on 37's or build a 30/8.8 with 35's on a smaller budget personally.
someone else will have better info.

 

29 spline 8.25, d44 or 8.8 should be fine on 35's. swapping the axle is a waste of time imo. aftermarket for the 8.25 has really taken off in recent years and has proven to hold up just fine on 35's

 

yeah but he was looking at a 30 spline upgrade and RCV's. which are overkill for D30 and way more expensive than swapping some already beefier axles
it's more of a waste of time to put that much into stock axles. but a 30/8.25 geared and locked with minor upgrades on 35's would be great yeah

 

agreed for your plans and what you'll be doing with it, keep the d30 and c8.25, you can throw 30 spline chromo shafts in the front if you want (RCVs are WAY overkill), and lockers front and rear.