oil pan differences

[Pinesdune]

I am just in the progress of putting together a list of all my stored parts that came with the truck I just brought home last fall. I have several oil pans, some early 28, some later ones. I've looked through the judging standards (old version) and seen when changes were made (omition of the bottom cleanout, drain holes in the baffle plate) I was just wondering how much (if any) the few changes made to just the oil pan helped to lenghthen engine life back in the day, and if anyone has any insight as to why certain changes were made, such as why omit the bottom cleanout.