I often wonder about a "Super Super VC10" with 2 RB211s..especially when they were reborn as tankers...
It would have been far more fuel efficient, maybe not as fast, but a quiet VC10? Nah...the lovely noise of those 4 RR Conways were part of the attraction!
When I was on holidayat Ascension, an engineer told me that a VC10 had a similar fuel burn to the Tristars just coming into service, but the Tristar could carry a lot more payload!
I can still remember waking up in the middle of the night in Crawley, hearing the ghostly howl of the British Caledonian VC10s winding down... Luvverly!