In first picture , notice how the PCV valve is routed into the oil filler cap on the driver side valve cover.
= SD only
In second picture , notice the cast characters "LS2" to the right of thermostat area = SD only
LS2 is the designation for SD455 engine ,,,, like Chevy had LS6 as a designation.
Also right next to thermostat area is a date code - for example K122 or E123 etc....
Third picture is where to find carburetor ID on driver side of carb.
This example is 17057274
