I think you might find your Datto will end up costing more than a Ferrari if you worry that much about rust. I tried my best to remove all of the rust I could from my shell.

Seriously, after you buy the new panels, get someone skilled to paint it, get someone skilled to retrim the interior, Get a decent engine going and finally get it all approved and register, you are looking at $35,000-$55,000 Australian Dollars, but a good proportion of this is paid skilled labour, so in the USA I don't expect that it would be much cheaper. Although they'd save some money on parts relative to their income.

Rust is nobody's friend. If you can't keep your car out of every bit of rain, and wipe down the car after every carwash, then removing all of the rust will be in vain.

To galvanise a datto completely would put maybe 10% more weight into it.

You need to do what I did, and find the straightest, rust free example, and start your work from there.

Remember that Red Mazda 929 guy? The guy who put a Cosmo 20B in it, and spent more than $110,000 on his rebuild, and he didn't bother to galvanise the body, why? Because doing any rebuild really isn't a cheap process.

Chris