Ok are theas Dodge Plymouth Chrysler. Or Desoto we I think they're factory https://www.ebay.com/itm/1956-58-Po...303/233490722204?_trksid=p2485497.m4902.l9144
Tread lightly on these........pretty sure these are early poly rather than later - not for the 1956 up 277-303- and later 318 Plymouth motor.
See if you can get a measurement/length from the guy....I can measure a poly 241 Dodge/Plymouth and poly 331 Chrysler after work.