Dennis,
When you say "dump tube" I assume are you referring to the one coming out of the block a bit ahead of the dip stick. With this setup you would normally use the type of oil filler cap that has no hose connected to it -- it "breathes" through the spaces between the upper and lower parts of the cap. Just clean the pot scrubber sponge in the cap from time to time. With this setup you should not get pressure build-up in the crank case to cause oil leaks. It would be more environmentally considerate to get one of those teardrop shaped oil traps (that is, if you don't already have one with the dump tube connected to it) and run a hose from there through a PCV valve into your intake manifold. If your manifold doesn't have a nipple on top to connect that hose to, you can replace the plug in the front end of the manifold with one. Then get an oil filler cap that will take a hose that you attach to your air filter, or to one of those adaptors that go between the filter and the carb. You can also switch the hoses, i.e., oil trap to air filter, and filler cap to manifold. In that case, I believe, (Someone, please, correct me if I'm wrong.) You need the oil trap that has a filter like a rolled up piece of brass foil inside the little pipe coming out of it. No PCV valve.
Bob S.
PS: Just saw that Joaquin beat me to the draw on this one with a hell of lot fewer words :-). Not for nothing do they call him "El Tigre Astuto y Veloz" where he lives.