I did the Genovese family earlier, now on to the Gambinos. If the membership seems low, that's because it is. The Genovese total was higher because Valachi was able to provide more information on his own family. Additionally, this is compatible with what the government knew at the time, explaining the inclusion of members we know were dead today, i.e. Mangano, Squillante, etc.

1963:

Estimated membership: 182 (I would probably estimate ~250 for the Gambinos at this time period - possibly more)

Boss: Carlo Gambino
Underboss: Joseph Biondo
Consiglieri: Joseph Riccobono

Caporegimes:
Amodeo, Joseph
Arcuri, Domenico
Castellano, Paul
Colozzo, Joseph
Conte, Pasquale
Dellacroce, Aniello
De Carlo, Calogero
Dongarra, Charles
Eppolito, James
Ferrara, Peter
Gambino, Joseph
Gambino, Paolo
Gennaro, Joseph
Leo, Arthur
Mascia, Angelo
Mazzie,Rocco
Paterno, Joseph
Russo, Gaetano
Scotto, Anthony
Sedotto, Anthony
Silesi, Joseph
Stincone, Peter
Traina, Giuseppe (Joseph)
Zappi, Ettore
Zingaro, Joseph

Soldiers:
Alberti, Andrew
Altamura, Thomas
Amato, *Unknown*
Amendolace, William
Amodeo, David
Anastasio, Anthony
Androlini, James
Angelo, John
Arcuri, Joseph
Armone, Joseph
Aronica, Edwardo
Avarello, Salvatore
Balsamo, Tito
Barcelona, Charles
Barese, Ernesto
Barranca, Frank
Barranca, Joseph
Barrata, Michael
Bassi, Hugo
Bellancia, Sebastiano
Benardo, John
Bisogno, Joseph
Bonadio, Paul
Bonfrisco, Salvatore
Bongiorno, Frank
Bonica, Edward
Bonino, Frank
Bonomo, Lawrence
Bove, Michael
Carminati, Anthony
Casablanca, Vincent
Castellana, Peter
Castore, Dominick
Chiri, Salvatore
Colao, Edward
Como, Louis
Coniglio, Nicholas
Consalvo, Carmine
Coppola, Joseph
Corrao, Vincent
Covello, Joseph
Crapanzano, Patsy
Crapanzano, Robert
Cuomo, Matthew
Cusimano, James
Cusimano, Joseph
D'Agostino, Louis
Dapolito, Frank
De Bene, Nicholas
De Cicco, Joseph
De Cicco, Vincent
De Fillippo, Louis
Dellacroce, Carmine
Delotro, Cataldo
De Vito, Ernest
Failla, James
Gagliardi, Frank
Galgano, Michael
Gallo, Joseph
Genese, Pasquale
Giardina, Joseph
Giardina, Louis
Giardina, Salvatore
Giordano, Joseph
Giuliano, Michael
Grammauta, Stephen
Granza, Anthony
Grieco, Orlando
Grillo, Leonard
Guglielmini, Frank
Guglielmini, John
Guglielmini, Joseph
Guglielmini, Salvatore
Iacovetti, David
Indelicato, Joseph
La Forte, Joseph
La Gana, Dominick
Laura, Pasquale
Leggio, Anthony
Li Calsi, Joseph
Licastri, Phillip
Lombardozzi, Anthony
Lombardozzi, Carmine
Lombardozzi, John
Lombardozzi, Paul
Lo Piccolo, Joseph
Lo Scalzo, Phil
Luciano, Frank
Mancuso, Aniello
Mancuso, Gennaro
Manfredi, Joseph
Mangano, Vincent (possibly deceased)
Mannino, Angelo
Mannino, Samuel
Marinelli, Accursio
Marino, Daniel
Masotto, Thomas
Massi, James
Meli, Angelo
Meli, Giosue
Meli, Philip
Melillo, Nicola
Moccardi, Frank
Modica, Frank
Modica, Philip
Mundo, Dominick
Muro, Sabbato
Palmieri, Frank
Palmieri, James
Palmieri, Vincent
Pasqua, Frank
Patti, Santo
Petito, Domenico
Piacenti, Peter
Piccolo, Frank
Pistone, Lawrence
Plate, Anthony
Quirolo, Edward
Ravo, Armando
Riccobono, John
Rizzo, John
Romano, Arnold
Rossi, Ugo
Ruggiero, Frank
Rumore, Louis
Rumore, Samuel
San Filippo, Paul
Santoro, John
Sarullo, Vincent
Scalise, Joseph (possibly deceased)
Scalise, Giacomo
Scalise, Giovanni
Scalise, Salvatore
Scandifia, Michael
Scarpulla, Giacomina
Scotto, John
Sedotto, Michael
Seru, Albert
Spallino, Anthony
Spitalieri, Alfonso
Spitalieri, Giosafat
Squillante, Vincent (possibly deceased)
Teti, Felice
Tocco, John
Todaro, Vincent
Torregrossa, Andrew
Torregrossa, John
Tortorella, Peter
Traina, Mario
Trapani, Salvatore
Tricardo, Michael
Vanella, Anthony
Zaccaria, Paul
Zappi, Anthony