In addition to the J13 Engine Gasket Set I ordered, I also ordered some gaskets from Moss Motors for the British B-series engine, found on the MGA and MGBs. Early Datsuns were produced with a licensed version of the B-series engine and the E-1 has that lineage, so many of the British engine parts cross over to the E-series engines.
I ordered two lines of valve cover gaskets from Moss, the first made of cork and the second a more durable silicone. The J13 valve cover gasket shown below at the top of both pictures is the one with the holes for the valve cover mounting screws, which is how the J13 and later (1964-65) 320s fixed their valve covers to the head. The earlier 320 valve covers did not have these six screws and were mounted by two large bolts through the top of the valve cover. The cork version is Moss Motors part #296-310 and was about $2. The red silicone version was part #296-311 and was $17.
The side cover/inspection cover gaskets that came with the J13 gasket set were made of cork. The same silicone valve cover gasket shown above from Moss also comes in a kit with a pair of red silicone inspection cover gaskets for less than $20 for all three pieces, part #296-425. Here are some shots of the J13 inspection cover gaskets compared to the B-series silicone versions.
Furthermore, Moss sells a very nice, U.S.-made exhaust manifold gasket that is a perfect match for the E-1 engine. Part #297-535 was $9. Compare to the J13 version below.