Garvino, rake adjustment couldn't get much simpler.... if you have the early 3-piece seats where the back removes from the seat base. These were stock on '71- early '73 Panteras. In that seat, there are two side bolts and two in back that hold it together. Take the back off and with a hacksaw, continue the back holes clear down the straps until you have two forks.
Reinstall the seat back, adjust the back for the rake you prefer and tighten the stock allen bolts up, being sure the washer is on the outside between the bolt head and fork.
For years, I carried a metric allen wrench in the car to adjust the back rake whenever Judy & I swapped seats, since I'm a foot taller.
Then I found 4 aluminum "tooling knobs" in a machine shop catalogue. I bored a recess in each knob for the stock allen bolt head, pressed a knob onto each bolt, crossdrilled through each knob & bolt-head for a roll pin to make a knob with a metric stud, and now I can adjust the seat rake while the Pantera is rolling, by simply untightening the knob's tensions, pulling on the seat back and re-tightening the knobs by hand. Sometimes, it's the little things that count; for instance a tiny bit more back-rake on a long trip.