What do you mean by PAL/NTSC? Do you mean also the colour encoding of the composite video output? If so, you have to change a lot more hardware than just Agnus.
The early A1000s that were sold here in Oz had PAL Agnus (so they generated PAL scan rates), but NTSC colour subcarrier oscillators and encoders, so they generated NTSC-like colour output.
I had to change the video clock crystal and then rebuild the chroma encoder. I did it some years ago on my A1000 and the results were not "broadcast quality", to say the least. It was watchable on a TV and for VCR use it was almost OK, but you'd use an RGB feed if you could.
I think you'll find that most TVs these days are "downwards-compatible" to accept the old-fashioned NTSC signal, anyway.
tony
