The potential problem is that combustion pressure from the exploding fuel/air mixture is making its way past the piston rings and into the crankcase. From there it could potentiall push oil out of the dipstick hole. An engine that has a cylinder or more with lower compression than the others could be a sign of bad rings, causing the aforementioned problem. The correct PCV (positive crankcase ventilation) will allow crankcase pressure/gas to vent to the intake manifold but ultimately that's not a cure for bad rings. So even if you have the correct dipstick and it fits correctly in the tube, it could still get pushed out or be prone to leaking if the rings are bad.
To answer your actual question, I don't know if my 258 dipstick has a gasket or not
I never really paid attention.