I just so happen to know of a near mint 78 510 wagon that is quite literally a barnfind. The guy who has it got it from his mom and dad's estate. His folks were the original owners. the car was painted once back in the early 90s, it was rear ended, but the bumper did it's job and took all the force and absorbed it with the bumper shocks, so it will need a new rear bumper. That is the extent of the body damage. It's been garaged it's whole life, so it's absolutely RUST FREE! it needs a fuel pump a battery and some gaskets and seals. I'm pretty sure it's an L20, but I could be wrong as I didn't get a great look at it and I am not that familiar with the older datsun engines.
I can go get some pics if you are SERIOUS about getting it. But, I have to warn you, the guy wants a mint for it. He's thinking in the $3000 and up. I think it's in need of a LOT more work than for it to be worth $3000, considering it's likely going to need all rubber suspension components replaced simply due to it's age.