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I tried looking through the Fourm and could not find anything on re-plating rusty nuts and bolts. I am restoring my 1938 8 cyl, model 1601 Packard and was wondering what rust protection (plating) should I use to re-plate the nut and bolts? Zinc, zinc nickel , use a chromate? What was used back in 1938?

To restore the car to as original as possible, what rust protection can I use and not get dinged if I ever have the car judged at a show?

Unless you own a plating service, it would be better to simply replace nuts, bolts, washers and the like with new ones of a better grade. Stainless would be cheaper than replating and would last longer without corrosion.

I don't think anyone loses points for doing that. However, if you had to have absolute original, you could take the originals to a metal stripper, re-install, and let them take another 80 years to rust. You could use section 50. of the parts book to figure out where they go after you get them back.

Some available bolts for convertibles may have to be modified to match the original which might be 1/8" shorter or have a longer shoulder. McMasters-Carr, Restoration Specialties, and other suppliers are easy to find and search online if your local Ace or Home Depot doesn't have. And Bruce Blevins has quite a catalog, plus he can make anything you need in that dept.

Joe's right. Why court the possibility of hydrogen-assisted cracking in 80-year-old fasteners holding a two-plus-ton automobile together for the sake of some clipboard-wielding cupcakes? I learned about this side effect of plating from a lifelong aero/auto machinist/mechanic pilot who worked on everything from his driven in the real world supercharged '37 Cord Phaeton to P-51 Mustangs and one of the only 18 P-40s still flying.

If they're still serviceable, just run them through the bead blast cabinet. (degrease, if oily, first) They'll look like new. Trim any heads that are edge warped with a file. I suspect not all will be usable,(extent of rust) but you'll have a better idea what to look for. Some of the manufacturers are no longer in business so sourcing certain logo stock is almost impossible without a donor or large parts cache.
Torqued fasteners require a certain percent thread engagement, so if threads are rusted out of tolerance, they need to be replaced - regardless. Do not reuse. Follow the service manual torque instructions.
Not a pre-war junkie, but I know from post war if zinc plated, they first changed bath composition in the early '60s, so today's bright plate is not correct for earlier. What I do is take new and just give them a light bead blast to knock the shine off and they look fine/indistinguishable.
If they're black oxide, there are ways to refinish, but I've never done, so I don't recommend things I don't do myself. They're also getting harder to find today but many available even square heads. Some were plain uncoated mild steel, too.

Eastwood sells a variety of different spray paints that can be used to dress-up bolts and bracketry. I've used their silver-cadmium paint will great results. I just media blasted everything with glass bead first, then painted them. Mostly just the bolt heads, washers, etc to avoid getting the threads mucked up.

You can see what it looks like in my project blog.