Engine manufacture date vs truck year model

[JKeopf]

Thanks to several in this group, I have been able to confirm what I suspected, that my engine is not original to my truck. I have a 1971 Stepside SWB, w/250 L6 engine. When working on the carb, throttle linkage & accelerator pedal, I found the linkage and pedal did not correspond to the original 71-72 configuration. The previous owner had glued the bottom of the floor mounted pedal to the floor mat. I installed the correct ball mount pivots, but began to wonder about the entire throttle setup. Now in looking at pre-formed engine tubing, I also found differences in '70 vs '71. Pulling from the block casting numbers and the stamped codes, I found it to be an 11/13/70 casting and 11/16/70 engine assembly. Otherwise it is the correct truck based engine. I don't know how the model year change over worked back then. My question is when shopping for engine parts, would these engine dates coincide with the '71 model year or are the throttle issues I found a good indication that other engine parts need to be for '70?