The best way to install a pan with these one piece gaskets is by this method.
First make sure you have the correct part number. The front and back rail are thicker than the four piece gasket set. Second, get just a little bit longer bolts for the corners(not necessarily the final bolt application). "On the four corners only", draw the pan towards the block evenly until the "final" rail bolts can be installed. After the rail bolts have been installed, you can go back and remove the corner bolts and install the proper legnth bolts for the final application. I have done a good number of these one piece gaskets and they work perfectly but the pan must be drawn evenly to the block by the four corners first. Bottomline, the gasket and pan must mate to the engine block as evenly as possible to eliminate leakage later.
The front and back rail gasket portion will bulge but that is okay as long as it is even. Hope that helps -Dave