First of all!
As for axle we need to know how deep your wallet is? 95% of us run the stock birfield axle! Now with Marlin's lower bearing caps that upgrades the bearings from 17mm to 25mm.
![King :king:](https://board.marlincrawler.com/Smileys/marlin/king.gif)
Or you can get the FJ80/60 axle, or buy a Diamond axle, or All-Pro's front Birf/D60, or a right diff D44/D60/D70. Then the Rockwell axle is possible.
Just start reading posts on some of our buildups!