FWIW, if the 235 configuration in the 3100 was the same as for the passenger car, the valve cover has forward oil fill/breather cap, no hose connection. See the image below from the '57 passenger assembly manual, p.65.
Unfortunately, I don't have the factory '57 truck assembly diagram, but perhaps others will, or an actual original vehicle for comparison.
My guess is for the trucks it is on the front ,Jim carter site says it was in the middle due to the hoods on vehicles having less height therefore moved to the middle.
Thanks, I hope some one has the truck diagram. The date codes are correct for 55 - 59 head and block. The casting numbers on the transmission are coming up as a 71. I'm in search of a correct tri 5 transmission. I just want to make it look as original as possible. I have had some people tell me the air breather is from a passenger car. Were they different? The engine and trans will be coming out next month for detailing / painting, and repairs to the speedometer drive gear.
For what it is worth, here is a picture of the 56. Forward oil fill, no hoses or pcv, and 2 screws per side holding it down. Not sure how much it changed for the 57 year model.
