Unfortunately, there's no engine assembly manual for '70s, but good news, the clips are shown in the electrical assemmbly manual. As books go, its probably the most worthwhile piece for restoring a '70.
There's 2 J clips that hold the wiring in place, the first on the farthest back and highest valve cover bolt driver's side valve cover, the second being on the second in from the back valve cover bolt (top row) on the passenger side valve cover. Clips are Ford Number 356640-S100, AMK had a VERY close substitute, that just needed a bit of bending to work. Two more of the same clips are used for the solenoid wire if you have AC, they go on the second and third in from the back valve cover bolts on the drivers side valve cover.
Carl