New to lowered suspension… What to use?

[derotoreut]

I'm looking to do a frame off on my '71 SWB and want to lower it. I'm thinking of around a 4/6 drop, probably 20" wheels, but want to know the right way to do it. I am thinking about using a new drop member with rack & pinion and coil overs in the front. For the rear I'm thinking about a 4-link with 9" rear end and coil overs. don't know if I need a C-notch or not? From what I've read I don't think so, but if the whole truck is removed from the frame, probably just as easy to do it. I appreciate any input. I'm definitely going to learn on this one.

This may sound crazy, but if I'm planning to go through all of this would I be better off with complete new chassis? By the time I add all of this to my existing frame it will add quite a bit.