Lowering issues

New to the dually scene. Not new to building Rides. This Web site was already help full in finding Western Chassis. I have to builds on the go. I don't need to reinvent the wheel. So you talent would appreciate! First build is a 1974 GMC Crew cab 3500hun. Looking to lower either 5&7 or the 6&8 kit. Any unforseen issues?. Second is a 1969 cab and chassis 1ton dually. Making my own fast and furious version. Has drum brakes up front .what options to lower.?? Will post photos of trucks. Thanks.