Replaced head and gasket.
New radiator.
New thermostat.
With an automatic trans, it kills the fun of it being a Datsun.
Loud is good.
Electricals has their problems.
And the solid rear axle (in the wagon) vs. IRS, kills the fun of it being a 510...
I owned 3 510's over the years. One of each body style. My favourite was 'Sherman', a green (Datsun green 939) 1971 wagon, which I bought with 87,000 miles, and reluctantly sold with 151,000 miles.
With a 4-speed and basic interior, I moved 2000 miles in it with half my furniture, baby equipment and a 2 month old behind my wife. All the while getting far better fuel economy than I deserved...