Thanx, ranchero Dan & Rancheroracer.
<>Thus far, some suspects have been eliminated: no holes in the hard lines, the flex line at the tank, the flex lines at the pump, or the line from pump to the filter; the flex vent line seems to be OK as far as my hand can reach on top of the tank. The next thing to check is the fuel pump [...do the easiest thing first] and the oil sump as you two have suggested. A carb leak is entirely possible and that will be checked in order. The saga continues, posts will come as things develop.
<>Another thing has crossed my mind: how/what determines how many gaskets should be placed between the carb and the manifold? Enough to make a good seal? Is the heat a factor in what thickness is used? Help!!