Stop in for a cup of coffee

You cant 1/2" dfferent in shaft lengths. But a 440 can be used in a 383 with a spacer.

Mopar Distributor identification guide by measuring shaft length, measured from mounting surface to lower end of distributor shaft.

Mopar LA engine – 3.875”
Mopar B engine – 3.5″
Mopar RB engine – 4″
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Chrysler 331/354 Hemi – 4.25″
Chrysler 392 Hemi – 4.5″
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Dodge 241/260/270 Hemi – 3.875”
Dodge 315/325 Hemi – 4.25″
Desoto 276/291 Hemi – 4.00″