Yeah, yeah, my bad. The ZX spindles do bring the wheels in 3/4". Sorry, brain fart. You can use the Z31 four lug hubs to put the offset back to 510 specs, but you will need z31 brake adapters, etc. Savag, one of the reasons people like the ZX setup is because the 3/4" offset difference. It allows you to tuck the wheels under the fenders better without flares; and retains the same, or similar offset from front to rear. The ZX spindle also uses bigger bearings.
Basically, the ZX is tried and true and inexpensive, which is the key when dealing with Datsun's. If you've got another solution, AWESOME, but make sure you consider end cost to the buyer when designing it.
More power to you for looking into new mod ideas.