My "new" '74 Duster- or why I need a project like a hole in the head

Really a good build. Well thought out and executed and some good ideas there.
Since you aren't a stranger to AFCO products, and if you want to adjust your rear height, consider adding some rear spring sliders and get rid of friction and 30 year old shackles to boot. Also negates the change in spring rate as the rear shackle moves through their arc. Depending on how you mount them you can alter your rear height too.
Read more than you probably want to know about them here. Happy reading!

Especially the Yellowbullet posts. Tons of good information to be found.

https://www.google.com/webhp?sourceid=navclient&ie=UTF-8#q=spring+sliders+yellowbullet+forum

Alan