Having seen what the speakers do to the door panels, I'd either put them in boxes under the front seats, suspended upside down under the dash or in the kick panel down by your feet. Look through the 120 gallery for some ideas.

I'm not familiar with the radio or antenna itself that you mention.

Some people have mentioned installing a new stereo underneath the existing stereo so that the original appearance is unchanged.

having new un-drilled fenders in my 67 220, I put the antenna horizontally in the engine bay.

I had thought that a flip-down cover made from a radio-delete plate might be a great way to conceal a modern CD ot MP3 player - especially if you already have a cut dash. Not exactly un-invasive...