Mopar Performance Distributor adjustable advance?
Here are some measurements of the keys. There are two styles of Mallory advance and I can't recall which these specs are for.
28 degrees, .496
26 degrees, .476
24 degrees, .458
22 degrees, .442
20 degrees, .424
18 degrees, .406
16 degrees, .390
Basically, every 2* is about .016-.018 change in width. 14* is going to be in the .372-.374 range
Here are some measurements from the other Mallory set. I believe these are the numbers for the OP's distributor.
Thickness of some keys from the mallory kit.
12* .125"
14*: .140"
16*: .155"
18*: .170"
20 0.185
22 0.205
Bust out those drill bit shanks!