Cool bike, I was lucky enough to be taken to Lance's shop by Ed in 1999. Lance was a really interesting guy and it was such a shame he died early in an industrial accident. I recall he used GCB forks and maybe shock/s on both Ed's Spondon and the custom Norton he'd built for Keanu Reeve which was in the shop at the time of my visit.
Regardless whether the mods work better or worse than an original, it's a little slice of history at a pretty cheap price IMHO. That GCB front end probably cost $16kusd alone when it was new. I remember Ed telling me some of the prices of the stuff that went into building his Spondon (funded by the original owner) and they were eye watering - the GCB gear prominent among it.