You can find the historical GDP data in the link.

Statistics-frequently requested data-national account-annual GDP

for some countries, the data back to year 1950 are available.

Another source is the book edited by Maddison (2003) "the world economy:historical statistics".for most counties in the world, data are available.The project I just finished uses the OECD data from this book, since I need more years.

I am not sure whether you can find this book. You may have to use OECD website to get your data.

Good luck