Galvanic compatibility with mild steel

Let me just get this out of the way: this is a total newbie question. But I appreciate any advice I can get!

I’m rebuilding / retrofitting a wood-and-steel trailer, and trying to identify affordable fasteners that won’t turn into solid lumps of rust. I live in a relatively dry area, but if there’s any moisture at all, it’s going to sprayed onto the underside of a trailer, along with road grime, salt, etc.

From everything I’ve found, the (readily available) materials that are most corrosion-resistant in their own right are stainless steel and hot dipped galvanized steel. However, I’m bolting onto/through a bunch of mild steel, and stainless is appreciably more anodic and than mild steel, while zinc (plating) is significantly more cathodic. Is this a problem? Is the zinc plating just meant to be sacrificial and shouldn’t worry about it? Am I looking at the whole question wrong?

I’m guessing I’m far from the first person to run into this question, but an hour communing with Google hasn’t gotten me very far. Any suggestions?