how to install upper control arm bushings

[vincesvintage]

I'm installing upper control arm bushings on a 1970 stang. The Ford shop manual states that a 6 15/16" inch spacer should be installed before pressing in bushings. The manual is WRONG. I have three 69-70's here and the spacing is over 8". I need to know the proper length of spacer. Help, Vince