Snapped the rear axel last night at the track

[Excidium28]

Edit: Snapped the rear driver side axel right before it connects to the cv joint on the wheel side. They have 28mm axels for auto and 38mm for manual but they both taper down to the same diameter where it connects to the cv joint, thats where it snapped. I have a 98 328i manual swapped with 99 M3 motor, tranny, rear diff (3.23 20%lsd). I lunched at 3k dropped the clutch, it hooked really good, felt a lil wheel hop and snap! Now I have 2 options

1. M3 uses the same axel but beefier cv joints, in order to install M3 cv joints I need to get the whole lower trailing arm.

2. The cheaper way, custom alloy race axels used for 1000hp cars, from what I understood just axels no cv joints. Now if the axel dont snap whats the next weak point cv joint?