These are available for a lot of engine families including the 385 series, FE, and even Pontiacs.
They are a one piece seal, but you have to slice through them with a sharp blade and then work them around the crankshaft. The crank is then dropped in and the cut goes to the top of the engine. They work ok, but honestly, I don't have any issues with the two-piece seal halves on FE's.