Byrd.....  Thank you for your post.  If I had a schematic of a Color Classic analog board, I could figure some of this out for my self, but I can not seem to find or buy any documentation.

For example, do you know what the vertical scan rate frequency is in the color classic before the VGA mod? And do you know what the vertical scan rate frequency is after the VGA mod?

I had no idea that one could roll in a 575 logic board and a 575 analog board into a color classic.  From what little I see posted, this would not push any component out of it's design spec.

jack the new kid