Modifications for a 4.5/6 drop?

[chevy72blu]

My truck was originally a 3/4 ton 72' C-20 and has since been converted to 1/2 ton. However, I still have the stock leaf spring rear and I'm having a hard time finding trailing arms, so this project is a ways off.

In the future though, I would like to go with a 4.5"/6" static drop. Can this be accomplished without C notching the frame and going to aftermarket x-member/control arms? Would 3.5"/5" be doable?

Thanks!