Do the whole thing at the same time (if you can afford to buy all the correct parts to do so). For a 3" to 3.5" front drop I would go 2 1/2 drop spindles and 1" drop front springs. I beleive ECE makes 5" drop coils.
Call ECE :
http://www.earlyclassic.com/ These guys are so helpful and will make you feel comfortable with what you are doing.
I went with ECE 2.5" drop spinds and 2" Ground force front drop springs, 4" ECE drop coils in the back. Truck has RAKE. Hope this helps.