Which of these criteria does your Miyata not meet? I'm not trying to be snide, just trying to get a sense of what you mean by the subjective traits like "robust".
The Miyata Pro pretty much covers all the bases, but it sure works well as my main road bike. I’m not sure I want to put bigger tires on it, though. It has a Tange Champion frame, so it is pretty robust. I am also working on building up a 1974 Raleigh International - would that frame be a viable candidate for my project? I have the frame but not the fork, so there is some latitude for how I can complete that. If the Raleigh International frame is a possibility, that might simplify the project. Possible?