What is this part

YES.make up a line ( 5/16) to the rad trans cooler fitting. Trace the lines to and from the trans to the rad and back to the trans. FYI they make universal inline filters in the $6 to $20 range. OR you can change your pan to the 64 and newer 904 pan with a dimpled pan floor to clear the in pan filter.64 and 65 trannys use a 2 port filter pickup. I do not have the number but the last one I got was from CarQuest Auto Parts.