1971 Chris Craft XK19 Floor Framing

I have a 71 Chris Craft XK19 - fiberglass hull, original wood floor. After 5 years of storage, the plywood floor and wood framing under it is dry rotted. The boat appears to have stringers encased in fiberglass that run bow to stern. The plywood floor sits on top of a 1 1/2 x 2 1/2 wood supports that run from the transom to just forward of the instrument panel. There are two supports, say 18"-24" apart, with three cross braces. The floor was glassed into the sides around the perimeter. What is a good current day wood (or other) choice to replace the framing? I had been referring to the framing as stringers and thought douglas fir was a good choice, but the more I think about it, I think they are more like floor framing members, so I don't think I need structural wood like fir, but definitely something for a marine application. Can I use pressure treated pine or similar? The fir will run approximately $150. Thanks, Tom