in case anyone finds this, I ended up getting a reasonable (relatively speaking) cost to upfare the ticket and not have to take the long odds of upgrades clearing.
The most curious thing I found was that on the return LHR - SFO the incremental cost to upfare from J to F was only $229. Kinda a no-brainer there, so I get to ride in the nose of a 747 one last time before United retires them.
Thanks for all the suggestions and tips.
Bob