I really miss my Univega GT, if not for an accident that bent the frame I would still be on it.

Unorthodox idea here. I ran panaracers, Bontrager hardcase, and a continental gatorskin in 27". All worked ok, the panaracers are a bit delicate IMO. Liked the bontragers best, but I live around a lot of flint, and always cut up sidewalls.
One time I started a four day trip, and cut the crap out of the rear Gatorskin on some debris(Rural Arkansas is not great for bicycle tires). Rather than waste time going back home, I stopped at a walmart and bought a 27" bell. Ran it for... Well, that was four years ago and its still in service. Its had a few flats, but so have almost every other tire Ive ever run.

If you want a better tire, cool. Im a little ashamed to admit to the world that the most reliable longest lasting tire I run came from walmart. But don't be alarmed with the tire width. I usually run a 32mm, and I weight more than you.

You might not have to much trouble putting a 700c wheelset on there, but if its got the short arm Dia-comp cantis, then it might be tight. See if you can borrow a 700c wheel to check if it looks like your brakes will work before getting a new set. Cant tell in the picture, but if thats a blueline suntour rear derailleur, it should handle a 32 tooth cog, I think I ran a 34 with one once.

And finally, bar ends are cool, and I use them, but downtube shifters work fine, and I use them on many of my bikes.