Tubes should be 1 3/4" some boiler tops had 2.25" tubes a 2 " round boiler brush on a 1 3/4" tube 2.5" on a 2.25"
for the cleanout door use either hi temp silicone or furnace cement stove gasket will work also.https://www.solobrushes.com/WebCatg1.asp?Cat1ID=4
Types of brushes
You can download the efm manual here Now if you have the older stoker that does not have the halfmoon sheet metal
plate with the thumb screw that covers the drum gear then you will have to adjust your feed by loosening the bolt on the gear arm that is connected to the gearbox on the bottom the arm will have a slot in it that you can move it up or down to increase or decrease the feed rate If you have the sheet meatal cover at the gear drum then turn the thumb screw and slide front or back to increase or decrease the feed .http://www.efmheating.com/d520.html