69 gmc lowering?

[rdrnation]

I have a 69 gmc 1/2 ton sb with coils in front and leaf springs in back. I want to do a 4/6 drop without cutting or c-notching the frame. i dont want a raked look, im looking for it to be level. Its also 6 lug and power drum brakes. I think it would probably be a good idea to change over to 5 lug and front disc brakes at the same time. need advice and suggestions on the best way to go about this. thanks