If you like your interior and it's color and you are saying it is in great shape then you could probably go with maybe a dark blue or white or something you feel will either match or set off your interior, the only issue I would have with those colors is with your choice of engine and suspension colors that to me kind of limits your exterior color choices to either red or black if you want everything to blend together like a well thought out project.
As far as the half vinyl removing it would not be that much work if you are prepping for paint anyways you would be half way there, and once it is gone it really opens up your paint options since you would no longer have to match it to anything.
When I got first my Monte it was a CL and had a black half vinyl on a black car and I was okay with it for a while until I laid out a game plan for the car and decided it wouldn't fit my future plans and still look right, also my original interior was light gray with 60/40 seats and needed replacing anyway and when I decided to redo my interior I seriously considered going black but then thought it would be too much black so I did everything in camel instead because I figured it would give it more contrast.
Now I'm not big on red cars either but I think a dark red without the half vinyl and a black interior would set off everything you have done to the rest of the car and tie it all together.
