Definitely a mark 4 engine, so yes it’s a 2 piece rear oil seal. Try your best to get your hands on an OEM GM seal, or at least FelPro or Victor Reinz, make sure the seal has helical serrations like a factory seal; some of the cheaper seals do not have this feature and will leak. Also offsetting the parting line of the seal from the main cap parting line will also help hold off leaks. I’m still a fan of the original GM style 4 piece pan gasket with the neoprene pan rails, stay away from cork, when installed properly they will not leak. I have seen some one piece pan gaskets leak. As an engine builder, my best advice for the future when getting your hands on any older/used engine is, at least pull the pan off , spot check a few rod & main bearings and install some new seals at minimum. Also look very closely at the surface on the crank where the seal rides, sometimes due to time there will be a grove or etching and no matter how many seals you throw at it, it will still leak. If this is the case, sometimes a polish will take care of it, or worse case, crankshaft replacement. Me on the other hand I would go through the entire engine and address anything that raises an eyebrow, to prevent any issues in the future, because who wants to do a job twice. Best of luck with your project.
