Technical Hemi dist and shaft

I pulled this dist. out of a 1957 IND 354 hemi that had been stored for 25 years. took out to prime engine, different than what I use to seeing . is it a conversion ? engine was all stock

 

Just Googled this and appears to be a 340 distributor going by webbed casting. I could be wring but those more knowledgeable can chime in. L-R OEM Hemi, OEM 340 and modified 340.


http://www.hotrodsandhemis.com/Rebuild/part3/HemiRebuildPart3.html

 

The two piece arrangement is factory for a number of industrial applications but mostly used in trucks.
The distributor you show is obviously a modified late model piece built to replace the mechanical advance/mechanical tach drive original.

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In addition to my 354 truck engine, I have seen that setup in 331/354 marine engines and some 361 industrial engines too. The distributor tang is offset so it fits together only one way.