This (BW film/paper spectrometry) is far more complicated that than just using a 361 or a blue filter, but in the same breath let me say that I think many of you are making this more complicated than it needs to be for making good pictures or calibrating PMK negs. Sure, most paper is sensitive to UV...and to blue and to green light. Stained negs block blue and some green more than other colors, so paper 'sees' a stained negative with higher density than a non-stained neg. We, humans, don't see blue light very well and nothing above about 400 nm (violet). We do see green quite well and then falling off in the other direction (red), too. Most glass and lenses don't transmit light past about 350nm, the big exceptions here are flourite lenses and reflective optics.
To precisely measure film density for calibration, one would need to know the spectral response of the paper you are using, the spectral transmission of all materials in the optical enlarging (or contact printing) path (not just the negative, but the lenses, glass carriers, plastic masks, VC filters etc.) and the spectral output of the light source. Once all this stuff is known, it is multiplied and integrated over the spectrum of interest and poof...the answer. Sound hard. It should. It is. And the question is, why bother? Take a picture, develop it, print it and is it too soft or too hard. Adjust development accordingly. Or use some of the calibration techniques in books. This takes care of all the variables in your system. If you must use a densitometer, and I do but I didn't for lots of years, use whatever you can afford. They all work. If the desitometer doesn't have the dynamic range to add a blue filter, just do it without and add 10% to the density. You will be so close that whether you have a 361 or 613 or xyz won't matter.
Take more pictures.