I joined BOAC in 1967 so my info is a bit distant
The -436 unless nearly empty wouldn't have made either LAX or SFO nonstop.
The SFO service was part of a transPacific routing to Tokyo ie LHR-JFK-SFO-HNL-(Wake Island)-HND-HKG
The LAX service was a terminator at the time and I think went via YUL, but didn't last very long - I think until the mid '60's
SFO was also used when we started the SYD service through the west but when the VC-10 took over that route then LAX came back on line, but still via JFK.
The -336 pax versions came in in the late '60's/early '70's and were used on the LAX non-stop routes - however initially we were always routed outbound via YWG,YYC or YUL and home via YOW - not that the aircraft couldn't make it but the cabin crew refused to!!!!!!!!
When that was sorted out we still went via (usually via YWG) outbound but nonstop homeward. The westbound stop had a hidden benefit - we could fill her up whereas nonstop would involve a payload penalty. Homeward bound no problemo! - 747's and DC10's solved all those problems!!