I've owned several vent rib TC barrels over the years, but I never removed the ribs on any of them and the only one I have now is a 21" .410 barrel. So this will be only a guess.
I seriously doubt there is a Weaver 2-hole base for your barrel. Scope mount bases that are made for TC barrels are all 4-hole or 6-hole. Whether the 2 holes you know you have will line up with 2 on a 4-hole base I don't know, but 2 screws wouldn't be much support. Could be if you take the rib off there are actually 4 holes hiding under it. If so a standard Weaver TC base would fit.