1970 Lowering/disc brake kit questions

[Cavscout]

Just got a 70 long bed and have been looking at replacing the front drum brakes and also lowering the truck.

1.) Is it better to spend the money on a brand new front disc conversion kit or go with used parts? New parts will last longer and should perform better but the used parts are much cheaper.

2.) I'm planning on running 20" wheels all the way around so how low should I go to make it look good? I don't want it slammed and I want to keep a level ride. I've noticed a lot of rear lowering kits have a frame c-notch kit, is that really needed?

Thanks in advance.