I think a 500 or a 750 would suit you well. The old 350's were fun, but they don't have enough power for highway use. When I get my RD200B back from the shop, it'll be strictly for putting around town off major streets. It tops out at 45 or 50 mph, so it's not going anywhere near a highway.

Don't shy away from the old 750's. Either my '82 CB750F or '81 GS1000G would have been good bikes for you. They are heavy machines by today's standards, close to 600 pounds, but they are solid, dependable rides. My biggest knock on the newer bikes is that even the smaller-displacement machines are tricked out with lots of expensive features, and to justify the cost, their engines are tuned within an inch of their lives to make lotsa power.

I put 96,000 km on the big FJ, and then had to decide whether to rebuild it or replace it. I looked around for a couple of years while I rode the ol' GS. I ended up putting $8000 into a complete rebuild of the FJ rather than drop close to $20,000 on a new machine that didn't suit me as well.