What repair manual for a 1970 duster?

For my 1970 Duster project I bought the factory service manual.To get the complete set you buy volume 1 and 2.It is listed as Plymouth service manual and covers the following models Belvedere,Fury,Barracuda,Valiant.They are more money than the haynes manual.The factory manual is going to be year specfic and far superior when it comes to technical info.