This might seem like a silly response, but...

If you want the look of 1970s Tri-X, Paul, perhaps simply cropping new Tri-X slightly will work.

If grain is finer and the image is sharper, slight cropping will reduce sharpness and increase grain. My guess is that gradation has improved along with these improvements, and will be commensurately reduced with cropping. If so, cropping (or alternatively using a slightly smaller format - e.g. half frame) might give you the equivalent of using 1970s film.

I realize that that will change perspective and such as well, but it might be the easiest answer.