General Motors Casting Number 3866983 Clutch Housing
3866982 (Ident. No. 3866983 ?)
0.683 HOUSING ASSEMBLY, Clutch
1965 ALL ST With 409 Engine (Chevy Full Size Parts Book)
3866982 Replaced 3843941 07-65
3866982 use 3872444 11-65
Most parts that I describe and picture, have identification on or with them, others I can identify from other sources and deduction (educated guess).
Factory correct applications are your responsibility. GM made part and part # changes with no rhyme but a reason (no production interruptions at any cost).
Applications 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!