General Motors Part Number 385056 Clutch Return Spring
0.846 EXTENSION, Return spring
65 W 29 only (1965 Cutlass Assembly Manual)
66 V-8 (1966 Cutlass Assembly Manual)
64-65 F85 330 (*1)
Factory correct applications are your responsibility. GM made part and part # changes with no rhyme but a reason (no production interruptions at any cost).
Application charts are for replacement parts that were available at the time of parts book printing, and when possible model specific assembly manuals.
My observations come from the parts I have in my collection or other reliable sources your parts may differ.
If Factory correctness is your goal, do more research, join car clubs,
forums and buy an assembly manual if one is available for your Project Car (you wont be sorry).
This is a fun and interesting part of the hobby!