I should add that I used my Rigol to scope the input and output lines on the BoB and verified correct signals at each end, when the BoB is not connected to the PC and is powered.
The resistors on PC side pins 10 and 13 are the only two that burned, and they still ohm correctly.
When I tested the setup later, the BoB was outside of the PC using a cable to connect to the PC (before it was installed on back-plate inside the PC and a ribbon cable to the internal LPT#3).
Later I swapped PCI ports.
Someone suggested that weak parallel chips cannot handle the current output of an SN74ACT chip.
I still cannot figure out what was making the burn, because it's not burning when outside the PC. The only difference is that I'm using USB 5V battery instead of that 40 amp 5V PC supply wire. At least, I think red is the 5V line. I did not bother to measure it.
Also, I moved the ribbon cable from LPT#3 header to the rear panel of the PC and tried that port as well.
For grins, this is the SW setup that I'm using:
https://cnc4pc.com/Tech_Docs/guide_for_MPG4_over_LPT2.htmI ordered a used MP9715P-2 card which is said to have a compatible chipset for this purpose, nv9805cv.