Don,
Good that it came out easy, mine too was painless.
The gas tank was painted M-177 Black Frame Paint. It is a semi-gloss paint. It is documented in The 1937 Ford Book, page A-13, from the V8 club.
I buy most of my parts from Joe's. He and the girls there are really good, nice people. I have always had a great experience with them, his prices are excellent and shipping is quick. Shout out to Joe!
I, too, have the early threaded filler pipe (wish I had the later one). It is prone to leaking, has been my experience. Be sure to order a couple of the lead washers for the filler pipe seal. I used two of them and it still leaks, grrrrrrrrrrrrrrr. I invested in a spanner wrench, specifically for the filler pipe notch spacing. It helps tremendously, and you don't have to bugger up the pipe by using some channel locks.
Let us know how it goes and if it leaks
gregg