Lowering dually, need advice

[502ss]

I just purchased an 84 crew cab 2wd dually. It's main purpose is to tow my 30' scarab boat but I want to lower it as much as possible while still maintaining function. I have read that you can't do a 6/8 without removing front inner fenders which I don't want to do. Can I get away with a 5/7 and not have to remove the fenders? For 7 in the rear I am guessing I still need to do a c-notch. Not sure of my tire combination yet, my plan is to let my clearance be the driver for which tires I go with. I do know the boat has about 800lbs of tongue weight so even lowered it still needs to carry some weight. Post some pics of different heights with a description of the height so I can see if a 5/7 will do!

Thanks