My suggestion is to get the block surface squeaky clean, including the threads where the bolts go, and choose a very sticky sealant. RTV does not fit this bill. It takes too long to cure and is not sticky enough to hold the gasket to the block.
Hotrod Lincoln has mentioned Permatex 300 in the past.
Make sure that the pan is not distorted where it meets the block by bolting the pan to the block without a gasket and check for gaps. Feeler gauge works well for this. You may need to do some tinsmith work to the sheet metal pan. Commonly you will find that you will need to hammer the metal where the bolts go through the pan to correct damage caused by prior over-torquing of the pan bolts.
Take a look at how the four gaskets fit together at the ends before applying any sealant. They interlock somewhat. It is not possible to keep these interlocks in place without a very sticky sealant long enough to instal the pan.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission