I have a 47 Plymouth. Is it necessary to take out the gas tank plug in order to have the tank cleaned out. It's a weird looking thing. Attached is a picture of it.

Did you ever get an answer to this question? I am new to the Antique Automobile Club of America Discussion Forum and I have a 1946 Dodge gas tank being cleaned by a radiator shop (rust boiled out, then lined). They didn't take this plug out before putting in a new lining. I took it to a second shop for another opinion and was informed that there is a "screen" that needed to be removed before the new lining was put in, which wasn't done, and that the plug you have attached as a pictured to your email is where (I think) the location of the screen is, so that is why I am asking whether you received an answer to your original post.
Thanks in advance for answering this post!
B.Hondle

Well, I cleaned out the tank myself, and recoated it with the tank kit from POR-15 (www.por15.com). I knew there was the oilite filter in it, but I took the chance.

So far, so good. No problem with the gas getting thru. Been driving it now for six months. Ed Parauka