One thing to consider is that, while the R20 frame is a gem, the forks are cheap. On an old bike, you can also get internal rusting. One of my worst crashes came when sprinting on an old bike with similar forks. Nothing worse than seeing the wheel twist to the right as you head for the pavement in slow motion!
I'm no framebuilder, but you definitely want to be careful with these kinds of mods. They say that steel warns before it fails, but that's not always true.