I believe the only operational L-1011 is Stargazer, N140SC operated by Orbital ATK, now owned by Northrop-Grumman. Its an ex-Air Canada L-1011-385-1, MSN 1067.
She originally had Rolls Royce RB211-22B engines but I believe has been re-engine with -524 models of higher power and far greater reliability. She is used for launching Pegasus rockets.