Parts book doesn't show size but it looks like it fits all the way up to 1975
70 Chevelle w /A ir Cond. (454),
70 Pass. w/C.A.C., A.T. (454),
70 Pass. w/Acc. Air Cond. (454),
71-72 All w /A ir Cond. (454),
73-75 All (454) ............................................. 3 9 3 7 7 8 7 1 12.90 PULLEY (3 groove) (Note 1)
NO TE 1 N o t u s e d o n m o d e ls h a v in g A c c . A i r Cond. a n d 2 .5 6 o r 2 .7 3 a x le ra tio .