I checked mine when it was running low 13's on street tires & a 4.10 gear. Saw they were just starting to twist after 1 1/2 years racing it & street duty. It was an E-body 8 3/4 rear narrowed. Put aftermarket with a sure grip & finally a spool.
IIRC in the NHRA rule book it says aftermarket axles required with a spool.