What would put me off doing it is this: Any bike of that vintage with steel rims is mostly braked by wishful thinking and your trainers, specially in the wet. To get it to stop in any meaningful way, you'd need to rebuild the wheels with alloy rims, certainly fit better brake shoes, and perhaps even dual pivot long reach brakes (shout out to followers of the Cult of Alhonga). I would do that on a Raleigh 20, and have done. I'd do it on a Moulton, or a Royal Enfield Revelation, but I would do it on that, because the resulting bike will still have all the stiffness of a wet noodle. Those things were like riding a drunk snake, and even as a fan of vintage bikes, I'd say most people would be better of with a $100 Wal Mart BSO than one of those. I know that's pretty damning, but really, they weren't very good bikes. Can it be done? Yes, absolutely. Should it be done? Only if you have genuine affection for the bike.