Backspacing help for 22" wheels...

[kyuss]

Hey there. I have a '67 with a porterbuilt front and custom rear with accuair setup. We measured between the rear brake drums in the back and came up with 56". I am planning on running a set of 22" - 8.5"/10" and really want to get the perfect back spacing. Have searched and searched this forum and looks like 5.75"ft/5"rear should be the ticket, but before I pull the trigger does anyone else with a bagged truck and narrow rear have any suggestions? Thanks much