@Carpenter: regarding NTSC to PAL60 conversions, this is generally easy to do. You only need to change the color pallets in your program to match the PAL60 pallet. PAL is often considered inferior to NTSC with regards to pallet selection, but you can change the colors based on lookup tables. The luminosity should only need minor tweaks, and you simply match the Hue on the PAL pallets close to the NTSC colors.
Unfortunately, the "rainbow" of colors is not evenly distributed like NTSC, and some colors such as pure yellow, are impossible to get right using the PAL color pallet. In the case of lemon yellow, you're stuck substituting it with either lime or orange. I'm honestly surprised Atari of Brazil went with NTSC TIAs for the PAL-M instead of PAL TIAs. I guess it worked out better that way since the rest of South America used NTSC, the ROMs would be the same. I imagine PAL50 Euro ROMs would have rolled on many of the old PAL60 CRTs same as they do in NTSC land.