Junkyard Dog,
Thanks for the response! Belatedly, in the Master Parts book 1929-48, I found part number 1515463 is for 1935-38 Gauge, Gasoline Tank, with Gasket. It includes FC, FD, and FA for 1936. I've still got to figure out the part naming patterns. One would think that since I work for a state agency would be better at that.

Sorry for pestering you all about the sending unit, sorry didn't discover in the first look in the parts book

!
But I'm still not sure about Question 2) I know that the different body styles used different filler necks, but did not know if any other differences.