Sounds like an FL .70. The 2 nipples on the silencer have different size holes. The nipple with the larger hole goes to the tank. The one with the smaller hole hooks to the nipple on the backplate. You can get a copy of the manual here:
http://manuals.hobbico.com/osm/fl-70-manual.pdf
You will have to pressurize the tank with the FL. It's an ABC engine meaning that the cylinder is tapered, and doesn't have a ring like the surpass. Therefore, it won't have the draw that the surpass has.