The links below lead to comma separated value files that each contain the Nino 3.4 SSTA time series for a series of model simulations. The vast majority of them have been extracted from Climate Variability Diagnostics Package and their data repositories. These are the result of the sterling effort of NCAR's Climate Analysis Section and should be cited as Phillips et al (2014). They've calculated the diagnostics for all the simulations that happened to be sitting on their server, so this is not an exhaustive collection (especially for the LGM). For simplicity, only the first ensemble member has been included on this files, but you're more than welcome to download the data other ensemble members from their website in netcdf format. The Pliocene ensemble dataset has been taken from Brierley (2015).
HadISST observed Nino 3.4 (1900-2010)
CMIP5 Historical Nino 3.4 (csv format)