Info a fellow HAMBer sent me shows that both the low deck DeSoto & the RB uses the same 4" length shaft. Get an RB dizzy & change out the counterclockwise reluctor for clockwise & there you go!
I've seen those on unmolested engines. I believe the 3/4 reach plugs were a more unique then, apparently Chrysler was worried some might install the more common 3/8 reach plugs.
After realizing knives are involved in a majority of all cutting injuries several companies have decided to reduce the use of knives and not let employees keep them in their pockets.