1968 Cuda 8 3/4 rearend axles

These may not be in stock, or maybe too expensive, but I believe they are what you're seeking.
A30-CST-A45 - A-Body, 8 3/4" Rear Axle Shafts, Stock A-Body Drum Brake (Redrilled) -- 30 (Pair) - Moser Engineering