The problem is that the modern, high output (up to 60% brighter) 60/55W bulbs are in the slightly smaller p43t fitting. . .
However, never fear, I know where to get adapter rings to fit in the p45t headlamp to take these bulbs. The new bulbs in their adapters have transformed the headlights on my GTD.
Incidentally, the guy who does these adapter rings also does high output multi-LED arrays for rear side/stop lights and indicator bulbs.
Go to
Paul Goff's website