When I bought a new "one-piece" pan gasket for my Corvette, it came with 4 plastic studs with slots in the end (for a screwdriver) and a "snap -thingy" (for want of a more technical term) on the side. These screwed into the pan bolt holes in the bottom of the block. Screw them in and simply push the pan (with gasket installed) up over the studs which depresses the "snap-thingy's" which then hold the pan in place so the rest of the bolts can be installed. Then using a screwdriver, remove the plastic studs and replace them with the regular pan bolts. Makes installing a pan with the engine in the car a snap and are even quite useful when the engine is not.
Why all of this verbiage for a Chevrolet part? Well, they use the same size pan bolts as a flathead Ford, and the plastic studs are robust enough to be used over and over. I have used my "Chevrolet studs" many more times installing flathead pans than the other.