The 311 # is for 69 cars. I don't think there are any L89's listed for 70.
From
http://www.camaros.org/drivetrain.sh...arAxleNumbers:
1970 axles had a C (for car) prefix added to the axle code. Most late 69 (after 08A) axles (10 or 12 bolt) were stamped using the 1970-style code, e.g. CBT instead of just BT.
For reference (since the VIN is not listed):
Seller: noom1108 in Delray Beach, Florida.
396/375 HP, Aluminum Heads (T0318CKU)
Cortez silver, black vinyl top, per trim tag (11427).
M-21 Muncie 4 speed (P0C20).
12 bolt Posi Trac, 4.10 gearing (CBW0305G)